The present invention relates to the art of a corrosion-resistant metal material and more particularly to a corrosion resistant alloy or coated base metal which is coated with a corrosion resistant alloy, which alloy is environmentally friendly, and has a long life.
As background material so that the specification need not specify in detail what is known in the art, U.S. Pat. Nos. 4,934,120; 4,982,543; 4,987,716; 4,934,120; 5,001,881; 5,022,203; 5,259,166; and 5,301,474 are incorporated herein by reference to illustrate metal roofing systems of the type to which this invention can be used. U.S. Pat. No. 5,455,122 is incorporated herein by reference to illustrate petroleum receptacles of the type to which this invention can be used. U.S. Pat. No. 5,203,985 is incorporated herein by reference to illustrate a prior art electroplating process which can be used to coat the coated base metal. U.S. Pat. Nos. 5,296,300; 5,314,758; 5,354;624; 5,395,702; 5,395,703; 5,397,652; 5,401,586; 5,429,882; 5,455,122; 5,470,667; 5,480,731; 5,489,490; 5,491,035; 5,491,036; 5,492,772; 5,520,964; 5,597,656; 5,616,424; 5,667,849,5,695,822; and 6,080,497 and U.S. patent application Ser. No. 07/913,209, filed Jul. 15, 1992; Ser. No. 08/042,649, filed Apr. 5, 1993; Ser. No. 08/929,623, filed Sep. 15, 1997; Ser. No. 08/980,985, filed Oct. 20, 1997; Ser. No. 09/100,578, filed Jun. 19, 1998; Ser. No. 09/131,219, filed Aug. 7, 1998; Ser. No. 09/161,573, filed Sep. 28,1998; Ser. No. 09/161,580, filed Sep. 28, 1998; and Ser. No. 09/420,165, filed Oct. 18, 1999 are incorporated herein by reference to illustrate various processes that can be used to coat, treat and use the coated base metal.
The present invention relates to the art of a corrosion-resistant metal materials such as a corrosion-resistant metal made of a corrosion-resistant metal alloy or a base metal which is coated with a corrosion resistant metal alloy, which corrosion-resistant metal material can be used in a wide variety of applications such as, but not limited to, architectural or building materials such as roofing materials, siding materials, window frames, sheet metal, metal plates and the like; truck and automotive products such as, but not limited to, gasoline tanks, filter casings, body molding, body parts and the like; household products such as, but not limited to, appliance housings, electrical housings, light fixtures and the like; marine products such as, but not limited to, boat hulls, boat masts, dock system components; and/or other types of metal materials such as, but not limited to, tools, machinery, wires, cables, electrodes, solder and the like. The invention also relates to various metal alloy or metal coating alloy compositions based upon metal alloys of tin and metal alloys of tin and zinc, and several novel methods and processes used therein for forming the metal alloy materials or base metals coated with the metal alloy materials, such as but not limited to, wire or solder forming, metal strip forming, and coated metal forming by a plating process and/or a hot-dip process (i.e plating of metal alloy and subsequent flow heating, immersion in molten metal alloy, metal spraying of metal alloy, and/or roller coating of metal alloy), pretreatment of the base metal prior to metal alloy coating, applying an intermediate barrier metal layer prior to metal alloy coating, post-treating the metal alloy or coated base metal, and/or forming the metal alloy or coated base metal into a variety of different articles.
Over the last several years, there has been a trend in the industry to produce products which are higher in quality, are environmentally friendly, and are safe for use by humans, animals, and/or plants. This push for quality, safety and environmental friendliness is very apparent in the automotive industry wherein both consumer groups and environmental organizations are constantly lobbying for safer, higher-quality vehicles that are more fuel efficient and less detrimental to the environment. Recycling old vehicles has been one answer to resolving the environmental issues associated with vehicles which have run out their useful life. Automotive salvage markets have developed for these vehicles. The vehicles are partially dismantled and sold as scrap metal wherein the metal is melted down and reformed into various parts. Because of the environmentally-un-friendly nature of lead, the gasoline tanks of vehicles must be removed prior to the recycling of the vehicle. Gasoline tanks are commonly made of carbon or stainless steel that are coated with a terne alloy.
Terne or terne alloy is a term commonly used to describe a metal alloy containing about 80% lead and the balance tin. The terne alloy is conventionally applied to a base metal by immersing the base metal into a molten bath of terne metal by a continuous or batch process.
Although terne coated metals have excellent corrosion-resistant properties and have been used in various applications, terne coated materials have been questioned due to environmental concerns based on the high lead content of the alloy. Environmental and public safety laws have been proposed and/or passed prohibiting or penalizing the user of materials containing a significant portion of lead. As a result, these terne coated gas tanks must be disposed of in dumping yards or landfills. Not only does the terne coated gasoline tank take up space in the landfills, but there is a concern with the lead leaching from the terne coating into the landfill site and potentially contaminating the surrounding area and underground water reservoirs. Plastic gasoline tanks have been used as an alternative to terne coated materials, but with limited success. Although the use of plastic tanks eliminates the environmental concerns associated with lead, the plastic in-of-itself is a non-environmentally-friendly compound which does not readily degrade and therefore must be disposed of in a landfill. The plastic used to make the gasoline tanks is usually not the type that can be recycled. Plastics have also been found to be less reliable than metal gasoline tanks with respect to durability and safety. Plastic gasoline tanks have a tendency to rupture upon impact, such as from a car accident, whereas a metal gasoline tank tends to absorb much of the shock on impact by bending and slightly deforming. Furthermore, the plastic gasoline tanks are more susceptible to being punctured from roadside debris since the plastic skin is not as strong or malleable as the skin of a metal gasoline tank. Plastic gasoline tanks also require new materials, special tools and new assembly methods to fix and install the gasoline tanks due to the nature of plastic and its physical properties. These additional costs and shortcomings of plastic tanks have resulted in very little adoption of plastic gasoline tanks in present day motor vehicles.
The lead content in metal materials is also of some concern for building materials. This is especially a concern when the metal materials are in contact with drinking water. In many countries lead pipe has been outlawed to reduce the amount of lead in the water. In many remote location throughout the world, piped water or well water is not readily available. As a result, structures, such as portable roof systems, are built to capture rain and to store the rain water for later use. These potable roof systems supply an important water source for inhabitants utilizing such structures. Roof systems that are designed to collect rain water are typically made of metal to increase the longevity of the roofing system. Typically, the roof systems are made of carbon steel since such metal is the least expensive. The carbon steel is commonly coated with a terne alloy to extend the life of the roof system. Terne alloy is commonly used due to its relatively low cost, ease of application, excellent corrosion-resistant properties and desirable colorization during weathering. Roof systems have been made of other metals such as, but not limited to, stainless steel, copper, copper alloys and aluminum. Stainless steel, copper, copper alloys and aluminum were typically not coated with a terne coating since these metals have excellent corrosion-resistant properties. However, in some limited applications, these metals were coated with terne to extend the life of these metals. However, as with lead piping, there is a concern that the lead in the terne coated roofing materials results in lead dissolving in the collected water.
Terne coated materials have typically been coated with a 6-8 lb. coating (7-11 microns), which is a very thin coating. This thin coating commonly includes pinholes. Terne coated materials that are drawn or formed in various types of materials such as, but not limited to, gasoline tanks, corrugated roofing materials and the like typically included one or more defects in the coating. The terne coating on the base metal designed to protect the base metal from corroding, thus comprising the corrosion resistance provided by the terne coating. Due to the thin layer of the terne coating and the pinholes in the coating, the coating on the base metal, upon being drawn by a die or by being formed tended to tear or shear the terne coating and/or elongate the pin holes on the coating thereby exposing the base metal. These exposed surfaces were subject to corrosion and over time compromised the structural integrity, safety and/or performance of the coated base metal. The non-uniform coating of stainless steel metal with the terne coating is especially evident since terne alloy does not bond as well to the stainless steel. Another disadvantage of using a terne alloy coating is the softness of the terne layer. The softness of the terne coating is susceptible to damage from the abrasive nature of forming machines and to environments that subject the terne coating to frequent contact with other materials.
Terne alloys have a further disadvantage in that the newly applied terne is very shiny and highly reflective. As a result, the highly reflective coating cannot immediately be used in certain environments, such as on buildings or roofing systems in or near airports and military establishments. The terne coating eventually loses its highly reflective properties as the components of the terne coating are reduced (weathered); however, the desired amount of reduction takes at least approximately 1xc2xd to 2 years when the terne coating is exposed to the atmosphere, thus requiring the terne metals to be stored over long periods of time prior to being used in these special areas. The storage time is significantly prolonged when the terne coated materials are stored in rolls and/or the terne alloy is protected from the atmosphere.
Metallic coatings such as tin or zinc have been tested as substitutes for terne coatings with limited success. The most popular process for applying a tin coating to a base metal is by an electroplating process. In an electroplating process, the coating thickness is very thin and typically ranges between 0.3 microns to 30 microns. The very thin thicknesses of the tin coating typically results in a tin coating having a network of small pinholes, thereby making the coated material generally unacceptable for use in corrosive environments, such as on building materials and automotive products. Such tin plated base metals can include a flash or intermediate metal layer (plated layer) to reduce the pinhole problems inherent with the tin plating process. The tin plated layer is also susceptible to flaking or being scrapped off when the tin plated base metal is drawn through a die and/or formed into various components. The flaking of the tin coating can also cause premature clogging of filter systems and liquid lines, such as in gasoline lines and filters when tin plated based metals are formed into gasoline tanks. The pinholes problem, flaking and/or scraping problem that is associated with plated tin coatings is very problematic since tin is not electroprotective under oxidizing conditions. Consequently, discontinuities in the plated tin coating result in the corrosion of the exposed base metal.
The plated tin coating of carbon steel is a well-known process in the food industry. However, in the specialized art of building materials, a tin coating for base metals for use on building materials and the like has recently been used as disclosed in U.S. Pat. No. 5,314,758. Tin coatings form a highly-reflective surface. As a result, materials coated with a tin coating cannot be used in an environment where highly-reflective materials are undesirable until the tin coated materials are further treated (i.e. paint) or the tin is allowed time to sufficiently oxidize.
Coating a base metal with zinc metal, commonly known as galvanizing, is another popular metal treatment to inhibit corrosion. Zinc is a desirable metal to coat materials because of its relatively low cost, ease of application, and excellent corrosion resistance. Zinc is also electroprotective under oxidizing conditions and inhibits or prevents the exposed metal, due to discontinuities in the zinc coating, from rapidly corroding. This electrolytic protection extends away from the zinc coating over exposed metal surfaces for a sufficient distance to protect the exposed metal at cut edges, scratches, and other coating discontinuities. Although zinc coatings bond to many types of metals, the bond is typically not very strong thereby resulting in the zinc coating flaking off the base metal over time and/or when being formed. The flaking of zinc, like the flaking of tin coatings, can cause premature clogging of filter systems and liquid lines when zinc coated base metal is formed into gasoline tanks. Further, when using fuel injection systems, the small particles of zinc or zinc oxide can disable the fuel injectors over time. Such problems are unacceptable in the automotive field. Zinc further does not form a uniform and/or thick coating when coating stainless steel thus resulting in discontinuities in the coating. Zinc is also a very rigid and brittle metal, thus tends to crack and/or flake off when the zinc coating is formed and/or drawn through a die. When zinc oxidizes, the zinc coating forms a white powdery texture (zinc oxide). This white powdery substance is undesirable for many building applications and in various other environments and applications. Consequently, the use of a tin or zinc coating as a substitute for terne coatings has not been highly reliable, or a cost effective substitute for traditional terne coatings.
Metal coatings that include tin and zinc have also been used to coated base metals. Electroplating a tin and zinc mixture onto a steel sheet is disclosed in Japanese Patent Application No. 56-144738 filed Sep. 16, 1981. The Japanese patent application discloses the plating of a steel sheet with a tin and zinc mixture to form a coating thickness of less than 20 microns. The Japanese patent application discloses that after plating, pin holes exist in the coating and subject the coating to corrosion. The pin holes are a result of the crystalline layer of the tin and zinc mixture slowly forming during the plating process. Consequently, the Japanese patent application discloses that the plated tin and zinc coating must be covered with chromate or phosphoric acid to fill the pin holes to prevent corrosion. The Japanese patent application discloses that a preplated layer of nickel, tin or cobalt on the steel sheet surface is needed so that the plated tin and zinc mixture will adhere to the steel sheet.
The coating of steel articles by a batch hot-dip process with a tin, zinc and aluminum mixture is disclosed in U.S. Pat. No. 3,962,501 issued Jun. 8, 1976. The ""501 patent discloses that the tin, zinc and aluminum mixture resists oxidation and maintains a metallic luster. The ""501 patent also discloses that the coating is applied by a batch process involving the immersion of a steel article into a molten alloy bath for an extended period of time. The ""501 patent also discloses that a molten tin and zinc metal alloy is very susceptible to oxidation resulting in viscous oxides forming on the surface of the molten tin and zinc metal alloy. These viscous oxides cause severe problems with the coating process. While the steel article is immersed in the molten alloy, a large amount of dross forms on the surface of the molten alloy. The dross results in non-uniformity of the coating and the formation of pin holes as the steel article is removed from the molten metal. The ""501 patent discloses that the addition of up to 25% aluminum to the tin and zinc metal alloy inhibits dross formation, prevents Znxe2x80x94Fe alloy formation, and reduces viscous oxide formation on the molten bath surface. The batch process disclosed in the ""501 patent subjects the surface of the article to differing residence times in the molten alloy which can result in differing coating thicknesses and coating properties on the coated article.
The treatment of a steel sheet by plating tin and zinc followed by heat flowing is disclosed in U.S. Pat. No. 4,999,258. The ""258 patent discloses a steel sheet plated with a layer of tin and a subsequent layer of zinc. The tin and zinc plated layers are then heated until the zinc alloys with the tin. The tin is applied at 0.2-1.0 g/m2 and the zinc is applied at 0.01-0.3 g/m2. The ""258 patent also discloses that when less than 1% zinc is used, the beneficial effect of the zinc is null; however, when more than 30% zinc is used, the coating will rapidly corrode under adverse environments. The ""258 patent also discloses that a nickel plated layer is preferably applied to the steel sheet prior to applying the tin and zinc plated layers to improve corrosion resistance. The heat treated tin and zinc layer can be further treated by applying a chromate treatment to the plated layer further improve corrosion resistance.
A continuous process for electroplating a carbon steel strip is disclosed in U.S. Pat. No. 5,203,985. The ""985 patent discloses that nickel is electroplated on a continuously moving strip of carbon steel. After the carbon steel has been nickel plated, the plated strip is hot dip coated with molten zinc.
The electroplating of tin, tin-nickel or tin and zinc by an electroplating process and subsequent formation of an intermetallic layer by heat flowing the plated layer is disclosed in U.S. Pat. No. 5,433,839.
Due to the various environmental concerns and problems associated with corrosion-resistant coatings applied to base metals and the problems associated with the inadvertent removal of the corrosion-resistant coating during the forming and/or drawing of the coated materials, there has been a demand for a coating or metal material that is corrosion-resistant, is environmentally friendly, and resists damage during forming into end components. Many of these demands where met by the tin metal alloy or the tin and zinc metal alloy and process and method for applying these alloys to a base metal which is disclosed in Applicants U.S. Pat. Nos. 5,314,758; 5,354,624; 5,395,702; 5,395,703; 5,397,652; 5,401,586; 5,429,882; 5,455,122; 5,470,667; 5,480,731; 5,489,490; 5,491,035; 5,491,036; 5,492,772; 5,520,964; 5,597,656; 5,616,424; 5,667,849. The present invention is an improvement or refinement of the alloys and/or use of the alloys disclosed in these prior patents.
The present invention relates to a product and method of producing a corrosion-resistant, environmentally friendly metal material. More particularly, the invention relates to a metal material that is at least partially composed of a corrosion resistant metal alloy, or the coating of a base metal with a corrosion resistant metal alloy which forms a corrosive-resistant barrier on the base metal. Even more particularly, the invention relates to a corrosion resistant metal alloy or a base metal coated with a corrosion-resistant metal alloy which corrosion resistant metal alloy or coated base metal is formed into truck and automotive products, architectural or building materials, household materials, marine products; and/or formed into tools, machinery, cable, wire, wire solder or welding electrodes.
In accordance with the principal feature of the invention, there is provided a corrosion resistant metal alloy primarily including tin or tin and zinc. In one embodiment of the invention, the corrosion resistant metal alloy is formed, molded and/or drawn into a metal article. In another embodiment of the invention, the corrosion resistant metal alloy is coated on a base metal, which coated base metal is formed, molded, and/or drawn into a metal article.
In accordance with one aspect of the invention, a metal alloy that primarily includes tin and zinc is a tin and zinc metal alloy. The tin and zinc metal alloy is a composite alloy wherein the tin and zinc constituents maintain their own integrity (structure or composition) in the composite with one phase metal being a matrix surrounding distinct globules or phases of the second phase metal. The tin and zinc system is a dual strata of metal globules or phases, each globule or phase being distinct from the other in structure or composition. The lowest weight percentage of zinc in an eutectic tin and zinc mixture is a tin rich mixture containing about 90-91 weight percent tin and about 9-10 weight percent zinc. For the tin rich matrix or phase and zinc rich globules or phases to form in a tin and zinc metal alloy, the zinc must make up at least over about 9-10 weight percent of the tin and zinc metal alloy. A zinc content over about 9-10 weight percent of the tin and zinc alloy results in the zinc precipitating out of the tin and forming zinc globules or phases within the tin and zinc metal alloy. The tin content of the tin and zinc metal alloy must be at least about 15 weight percent of the tin and zinc metal alloy so that there is a sufficient amount of tin within the tin and zinc metal alloy to form the tin phase about the zinc phase. A metal alloy that primarily includes tin and zinc but has a zinc content that is equal to or less than the minimum eutectic weight percentage of zinc is not a tin and zinc metal alloy. As defined herein, a tin and zinc alloy is a metal alloy that includes at least about 15 weight percent tin and at least about 10 weight percent zinc and the tin content plus zinc content of the metal alloy constitutes at least a majority of the metal alloy. One of the important and desirable properties of the tin and zinc metal alloy is its excellent corrosion-resistance in many different environments. The tin and zinc metal alloy is very corrosion resistant in marine environments wherein chloride salts are common, and in industrial environments wherein sulfur and sulfur compounds are present. The excellent corrosion-resistance of the tin and zinc metal alloy is believed to result from the formation of a stable, continuous, adherent, protective film on the surface. The damaged film generally reheals itself quickly. Because of the general inertness of the film, that is at least partially formed of tin and zinc oxide, in most atmospheres, the corrosion resistant tin and zinc metal alloy is considered to be environmentally safe and friendly, and considered a safe material to be used in the human environment. The tin and zinc metal alloy also forms a dull, low-reflecting surface; has a pleasing color; performs well in low temperatures; has a relatively low coefficient of thermal expansion; resists degradation by solar energy; can be molded, cast, formed, drawn, soldered, painted and/or colored; and/or can be installed in a variety of weather conditions. The tin and zinc metal alloy is further a cost effective material for use in structures used in corrosive environments such as in the tropics and other areas where buildings are exposed to strong winds, corrosive fumes, and/or marine conditions. The tin and zinc metal alloy can also be used as a solder and/or wire electrode. In one embodiment of the invention, the tin content plus the zinc content in the tin and zinc metal alloy makes up over 50 weight percent of the tin and zinc metal alloy. In one aspect of this embodiment, the tin content plus the zinc content in the tin and zinc metal alloy is at least about 60 weight percent of the tin and zinc metal alloy. In another aspect of this embodiment, the tin content plus the zinc content in the tin and zinc metal alloy is at least about 75 weight percent of the tin and zinc metal alloy. In yet another aspect of this embodiment, the tin content plus the zinc content in the tin and zinc metal alloy is at least about 80 weight percent of the tin and zinc metal alloy. In still yet another aspect of this embodiment, the tin content plus the zinc content in the tin and zinc metal alloy is at least about 85 weight percent of the tin and zinc metal alloy. In a further aspect of this embodiment, the tin content plus the zinc content in the tin and zinc metal alloy is at least about 90 weight percent of the tin and zinc metal alloy. In yet a further aspect of this embodiment, the tin content plus the zinc content in the tin and zinc metal alloy is at least about 95 weight percent of the tin and zinc metal alloy. In still a further aspect of this embodiment, the tin content plus the zinc content in the tin and zinc metal alloy is at least about 98 weight percent of the tin and zinc metal alloy. In still yet a further aspect of the embodiment, the tin plus zinc content in the tin and zinc metal alloy is at least about 99 weight percent of the tin and zinc metal alloy.
In accordance with another aspect of the invention, a metal alloy that primarily includes tin and equal to or less than the minimum eutectic weight percentage of zinc, when zinc is included in the metal alloy, is a tin metal alloy. As defined herein, a tin metal alloy is a metal alloy that includes at least a majority of the metal alloy and includes less than 10 weight percent zinc, when zinc is included in the metal alloy. The corrosion resistant tin metal alloy forms a corrosion resistant coating that protects the surface of the base metal from oxidation. The corrosion resistant tin metal alloy provides protection to the base metal in a variety of environments such as rural, industrial, and marine environments. The corrosion resistant tin metal alloy also performs well in low temperatures; has a relatively low coefficient of thermal expansion; has a pleasing color; resists degradation by solar energy; can be molded, cast, formed, drawn, soldered, painted and/or colored; and/or can be installed in a variety of weather conditions. Because of the relative inertness of the tin oxide in many environments, the corrosion resistant tin metal alloy is considered to be environmentally safe and friendly and considered a safe material to be used in the human environment. The corrosion resistant tin metal alloy is also a cost effective material for use in structures erected in corrosive environments, such as in the tropics and other areas where buildings are exposed to strong winds, corrosive fumes, and/or marine conditions. The tin metal alloy can be used as a solder and/or wire electrode. In one embodiment of the invention, the tin content in the tin metal alloy makes up over 50 weight percent of the tin metal alloy. In one aspect of this embodiment, the tin content in the tin metal alloy is at least about 75 weight percent of the tin metal alloy. In another aspect of this embodiment, the tin content in the tin metal alloy is at least about 80 weight percent of the tin metal alloy. In yet another aspect of this embodiment, the tin content in the tin metal alloy is at least about 85 weight percent of the tin metal alloy. In still yet another aspect of this embodiment, the tin content in the tin metal alloy is at least about 90 weight percent of the tin metal alloy. In a further aspect of this embodiment, the tin content in the tin metal alloy is at least about 95 weight percent of the tin metal alloy. In yet a further aspect of this embodiment, the tin content in the tin metal alloy is at least about 98 weight percent of the tin metal alloy. In still a further aspect of this embodiment, the tin content in the tin metal alloy is at least about 99 weight percent of the tin metal alloy.
In accordance with yet another aspect of the invention, the corrosion resistant tin metal alloy and corrosion resistant tin and zinc metal alloy contain a low lead content. The lead source in the tin metal alloy or the tin and zinc metal alloy can be from impurities in the raw tin and/or zinc ore used to make the metal alloy, and/or can be from directed additions of lead to the metal alloy. In some metal alloy combinations, lead in the metal alloy positively affects one or more physical and/or chemical properties of the metal alloy. Metal alloys that include little or no lead are considered more environmentally friendly, and the prejudices associated with high lead containing alloys are overcome. In one embodiment of the invention, the tin metal alloy and the tin and zinc metal alloy includes no more than about 10 weight percent lead. In one aspect of this embodiment, the metal alloy includes less than about 2 weight percent lead. In another aspect of this embodiment, the metal alloy includes less than about 1 weight percent lead. In yet another aspect of this embodiment, the tin metal alloy and the tin and zinc metal alloy includes less than about 0.5 weight percent lead. In still another aspect of this embodiment, the metal alloy includes less than about 0.05 weight percent lead. In still yet another aspect of this embodiment, the metal alloy includes less than about 0.01 weight percent lead.
In accordance with a further aspect of the invention, the tin metal alloy and tin and zinc metal alloy include one or more additives. In one embodiment of the invention, the one or more additives generally constitute less than about 25 weight percent of the metal alloy. In one aspect of this embodiment, the one or more additives constitute less than about 10 weight percent of the metal alloy. In another aspect of this embodiment, the one or more additives constitute less than about 5 weight percent of the metal alloy. In yet another aspect of this embodiment, the one or more additives constitute less than about 2 weight percent of the metal alloy. In still another aspect of this embodiment, the one or more additives constitute less than about 1 weight percent of the metal alloy. In still yet another aspect of this embodiment, the one or more additives constitute less than about 0.5 weight percent of the metal alloy. In another embodiment of the invention, the additives include, but are not limited to, aluminum, antimony, arsenic, bismuth, boron, bromine, cadmium, carbon, chlorine, chromium, copper, cyanide, fluoride, iron, lead, magnesium, manganese, molybdenum, nickel, nitrogen, phosphorous, potassium, silicon, silver, sulfur, tellurium, titanium, vanadium, and/or zinc. The one or more additives included in the corrosion resistant metal alloy are used to enhance the mechanical properties of the alloy, to improve corrosion resistance of the metal alloy, to improve grain refinement of the metal alloy, to alter the color of the metal alloy, to alter the reflectiveness of the metal alloy, to inhibit oxidation of the metal alloy during forming or coating of the metal alloy and/or when the metal alloy is exposed in various types of environments, to inhibit dross formation during the forming or coating of the metal alloy, to stabilize one or more components of the metal alloy, to improve the bonding of the metal alloy on the base metal and/or intermediate barrier metal layer on the base metal, to improve the flowability of the metal alloy during the forming or coating process, to produce the thickness of heat created intermetallic layer, and/or to reduce or inhibit the crystallization of the tin in the metal alloy. The inclusion of one or more additives in the corrosion resistant metal alloy preforms one or more of the above listed functions and/or features in the metal alloy. The believed functions and features of select additives are described below; however, the described additives may have additional functions and features. Aluminum reduces the rate of oxidation of the molten metal alloy; reduces dross formation during the coating process; alters the reflective properties of the metal alloy; alters the mechanical properties of the metal alloy (i.e. coatability, durability, flexibility, flowability, formability, hardness, and strength); and/or reduces the thickness of the heat created intermetallic layer to improve the formability of the coated base metal. Antimony, bismuth, cadmium, and/or copper prevents or inhibits the crystallization of the tin in the metal alloy, which crystallization can weaken the bonding and/or result in flaking of the corrosion resistant metal alloy; improves the bonding properties of the metal alloy to the base metal and/or intermediate barrier metal layer; alter the mechanical properties of the metal alloy; and/or alters the corrosion resistant properties of the metal alloy. Only small amounts of antimony, bismuth, cadmium, and/or copper are needed to prevent and/or inhibit the crystallization of the tin. This small amount can be as low as about 0.001-0.05 weight percent, and typically as low as 0.001-0.004 weight percent. Arsenic alters the mechanical properties of the metal alloy. Cadmium, in addition to its bonding, corrosion resistant, stabilizing and/or mechanical altering properties, reduces the rate of oxidation of the molten metal alloy; reduces dross formation during the coating or forming process of the metal alloy; alters the color and/or reflective properties of the metal alloy; and/or improves the grain refinement of the metal alloy. Chromium provides additional corrosion protection to the metal alloy; alters the mechanical properties of the metal alloy; and/or alters the color and/or reflective properties of the metal alloy. Copper, in addition to its corrosion resistant, stabilizing and/or mechanical altering properties, alters the color and/or reflective properties of the metal alloy. Iron alters the mechanical properties of the metal alloy; and/or alters the color of the metal alloy. Lead provides additional corrosion protection to the metal alloy; alters the mechanical properties of the metal alloy; alters the color of the metal alloy; and/or improves the bonding properties of the metal alloy to the base metal and/or intermediate barrier metal layer. Magnesium alters the mechanical properties of the metal alloy; reduces the anodic characteristics of the metal alloy; reduces the rate of oxidation of the molten metal alloy; and/or reduces dross formation during the forming or coating process of the metal alloy. Manganese provides additional corrosion protection to the metal alloy; improves the grain refinement of the metal alloy; and/or improves the bonding properties of the metal alloy to the base metal and/or intermediate barrier metal layer. Nickel provides corrosion protection to the metal alloy, especially in alcohol and chlorine containing environments; alters the mechanical properties of the metal alloy; and/or alters the color and/or reflective properties of the metal alloy Silver alters the mechanical properties of the metal alloy; and/or alters the color and/or reflective properties of the metal alloy. Titanium improves the grain refinement of the metal alloy; alters the mechanical properties of the metal alloy; provides additional corrosion protection to the metal alloy; reduces the rate of oxidation of the molten metal alloy; reduces dross formation during the forming or coating process of the metal alloy; alters the color and/or reflective properties of the metal alloy; and/or improves the bonding properties of the metal alloy to the base metal and/or intermediate barrier metal layer. Zinc alters the mechanical properties of the metal alloy; provides additional corrosion protection to the metal alloy, alters the color and/or reflective properties of the metal alloy; improves the bonding properties of the metal alloy to the base metal and/or intermediate barrier metal layer, and/or stabilizes the tin to inhibit or prevent crystallization of the tin in the metal alloy.
In accordance with another aspect of the invention, the thickness of the corrosion resistant metal alloy is selected to provide the desired amount of corrosion resistant protection to the surface of the base metal. Generally thinner coating thicknesses can be obtained by a plating process and thicker coating thicknesses can be obtained by immersion in molten metal alloy. The selected thickness of the coating will typically depend on the use of the coated base metal and the environment the coated base metal is to be used. A 6 lb. coating on a base metal is a common thickness for a thin coating. A 6 lb. coating has a coating thickness of about 7 microns. A 6 lb. coating is commonly applied by a plating process. In many instances, very thin coating thickness includes one or more pin holes in the coating. A 40 lb. coating on a base metal is also a common coating having a thickness of about 50 microns. A 40 lb. coating typically has few, if any, pin holes, and due to the thicker coating, resists tearing when the coated metal strip is drawn or formed into various types of components. Thicker metal alloy coatings are commonly used for automotive components (i.e. gasoline tank shell members), and roofing and siding materials. In one embodiment of the invention, the metal alloy coating is applied by a single plating process. In one aspect of this embodiment, the thickness of the metal alloy coating is at least about 1 micron. In another aspect of this embodiment, the thickness of the metal alloy coating is at least about 2 microns. In still another aspect of this embodiment, the thickness of the metal alloy coating is about 2-30 microns. In another embodiment of the invention, the metal alloy coating is applied by a) multiple plating processes, b) single or multiple hot-dip processes, and/or c) at least one plating process and at least one hot dip process. In one aspect of this embodiment, the thickness of the metal alloy coating is at least about 1 micron. In another aspect of this embodiment, the thickness of the metal alloy coating is up to about 2550. In still another aspect of this embodiment, the thickness of the metal alloy coating is about 2.5-1270 microns. In yet another aspect of this embodiment, the thickness of the metal alloy coating is about 7-1270 microns. In still yet another aspect of this embodiment, the thickness of the metal alloy coating is about 7-1250 microns. In a further aspect of this embodiment, the thickness of the metal alloy coating is about 15 to 1250 microns. In yet a further aspect of this embodiment, the thickness of the metal alloy coating is about 25-77 microns. In still a further aspect of this embodiment, the thickness of the metal alloy coating is about 25-51 microns.
In accordance with still another aspect of the invention, the base metal is a metal strip. A xe2x80x9cstripxe2x80x9d is defined as metal in the form of a thin metal sheet that is or can be rolled into a roll of metal, as opposed to plates of metal or other configurations of the metal. Metal strip which has a thickness of less than about 127 microns (0.005 inch) can break as the strip is pretreated and/or coated with a metal alloy coating at high process speeds. A high process speed is defined as a metal strip moving through the pretreatment process, intermediate barrier metal coating process and/or metal alloy coating process at a speed of about 60-400 ft/min. However, the metal strip thickness should not be too great so as to prevent the strip from being able to be directed, at a relatively high speed, through the pretreatment process, if any, and the coating process. Metal strip which is too thick is more difficult to heat when a heat created intermetallic layer is to formed between the base metal and metal alloy coating and/or intermediate barrier metal, especially when the metal strip is moving at high speeds and/or coated over a short period of time. Metal strips having too great of thickness are also difficult to maneuver at economical high speeds through the pretreatment process, if any, and the coating process. In one embodiment of the invention, the thickness of the metal strip is thin enough such that the metal strip can be unrolled from a roll of metal, coated by a metal alloy coating, and re-rolled into a roll of coated metal strip. In one aspect of this embodiment, the thickness of the metal strip is not more than about 5080 microns. In another aspect of this embodiment, the thickness of the metal strip is less than about 2540 microns. In yet another aspect of this embodiment, the thickness of the metal strip is less than about 1270 microns. In still another aspect of this embodiment, the thickness of the metal strip is less than about 762 microns. In a further aspect of this embodiment, the thickness of the metal strip is about 127-762 microns. In yet a further aspect of this embodiment, the thickness of the metal strip is about 254-762 microns. In still a further aspect of this embodiment, the thickness of the metal strip is about 381-762 microns. In yet a further aspect of this embodiment, the thickness of the metal strap is about 127-381 microns. In still yet a further aspect of this embodiment, the thickness of the metal strip is about 508-762 microns. In another embodiment of the invention, the thickness of the metal strip is not more than about 1588 microns when the metal strip is formed of stainless steel, carbon steel, nickel alloys, titanium or titanium alloys. These types of metal strip are difficult to maneuver at economical, high speeds through the coating process when the metal strip thickness is greater than 1588 microns. In one aspect of this embodiment, metal strip made of stainless steel, carbon steel, nickel alloys, titanium or titanium alloy strip has a thickness of about 255-762 microns.
In accordance with still yet another aspect of the invention, the base metal is a metal plate. In one embodiment of the invention, the metal plate is a rectangular or square metal plate having a length of about 1 to 15 feet and a width of about 1-20 feet. In another embodiment of the invention, the thickness of the metal plate is not more than about 51000 microns (2 inches). In one aspect of this embodiment, the thickness of the metal plate is not more than about 25400 microns. In another aspect of this embodiment, the thickness of the metal plate is not more than about 12700 microns. In still another aspect of this embodiment, the thickness of the metal plate is not more than about 1270 microns. In yet another aspect of this embodiment, the thickness of the metal plate is about 127-5080 microns. In still yet another aspect of this embodiment, the thickness of the metal plate is about 127-1270 microns. In a further aspect of this embodiment, the thickness of the metal plate is about 127-381 microns.
In accordance with another aspect of the invention, the base metal is carbon steel. In one embodiment of the invention, the carbon steel base metal is a metal strip. In one aspect of this embodiment, the thickness of the carbon steel strip is less than about 2540 microns. In another aspect of this embodiment, the thickness of the carbon steel strip is less than about 1588 microns. In yet another aspect of this embodiment, the thickness of the carbon steel strip is less than about 1270 microns. In still another aspect of this embodiment, the thickness of the carbon steel strip is up to about 762 microns. In a further aspect of this embodiment, the thickness of the carbon steel strip is about 127-762 microns. In yet a further aspect of this embodiment, the thickness of the carbon steel strip is about 254-762 microns. In still a further aspect of this embodiment, the thickness of the carbon steel strip is about 381-762 microns. In another embodiment of the invention, the carbon steel base metal is a metal plate.
In accordance with still another aspect of the invention, the base metal is stainless steel. xe2x80x9cStainless steelxe2x80x9d is used in its technical sense and includes a large variety of ferrous alloys containing chromium and iron. Carbon steel base metal that is plated with chromium and subsequently coated with a metal alloy coating by a hot dip process transforms the carbon steel into stainless steel at least at the surface of the base metal surface. The stainless steel may also contain other elements or compounds such as, but not limited to, nickel, nickel alloys, carbon, molybdenum, silicon, manganese, titanium, boron, copper, aluminum and various other metals or compounds. Elements such as nickel can be flashed (plated) onto the surface of the stainless steel or directly incorporated into the stainless steel. In one embodiment of the invention, the stainless steel base metal is 304 or 316 stainless steel. In another embodiment of the invention, the stainless steel base metal is a metal strip. In one aspect of this embodiment, the thickness of the stainless steel strip is less than about 2540 microns. In another aspect of this embodiment, the thickness of the stainless steel strip is less than about 1588 microns. In yet another aspect of this embodiment, the thickness of the stainless steel strip is less than about 1270 microns. In still another aspect of this embodiment, the thickness of the stainless steel strip is up to about 762 microns. In a further aspect of this embodiment, the thickness of the stainless steel strip is about 127-762 microns. In yet a further aspect of this embodiment, the thickness of the stainless steel strip is about 254-762 microns. In still a further aspect of this embodiment, the thickness of the stainless steel strip is about 381-762 microns. In still another embodiment of the invention, the stainless steel base metal is a metal plate.
In accordance with yet another aspect of the invention, the base metal is copper. Copper metal is known for its malleability properties and natural corrosion resistant properties. Copper metal that is coated with a metal alloy can be formed in a variety of simple and complex shapes. In one embodiment of the invention, the copper base metal is a metal strip. In one aspect of this embodiment, the thickness of the copper strip is not more than about 5080 microns. In another aspect of this embodiment, the thickness of the copper strip is less than about 2540 microns. In yet another aspect of this embodiment, the thickness of the copper strip is less than about 1270 microns. In still another aspect of this embodiment, the thickness of the copper strip is up to about 762 microns. In a further aspect of this embodiment, the thickness of the copper strip is about 127-762 microns. In yet a further aspect of this embodiment, the thickness of the copper strip is about 254-762 microns. In still a further aspect of this embodiment, the thickness of the copper strip is about 381-762 microns. In still another embodiment of the invention, the copper base metal is a metal plate.
In accordance with still yet another aspect of the invention, the base metal is a copper alloy. xe2x80x9cCopper alloysxe2x80x9d as used herein include, but are not limited to, brass and bronze. Brass is defined as a copper alloy that includes a majority of copper and zinc. Bronze is defined as an alloy that includes tin and a majority of copper. Brass and bronze are copper alloys with known corrosion resistant properties in various environments. Although brass and bronze are relatively corrosion resistant in many environments, brass and bronze are susceptible to a greater degree of corrosion in some environments than others. Brass and bronze are also relatively bright and reflective materials which can be undesirable for use in several applications. As a result, it has been found that brass and bronze coated with a corrosion resistant metal alloy can overcomes these deficiencies. In one embodiment of the invention, the copper content of the brass is about 50.1-99 weight percent and the zinc content is about 1-49.9 weight percent. In one aspect of this embodiment, the brass includes one or more additives such as, but not limited to, aluminum, beryllium, carbon, chromium, cobalt, iron, lead, manganese, magnesium, nickel, niobium, phosphorous, silicon, silver, sulfur, and/or tin. These additives typically alter the mechanical and/or corrosion resistant properties of the brass. In another embodiment of the invention, the bronze includes one or more additives such as, but not limited to, aluminum, iron, lead, manganese, nickel, nitrogen, phosphorous, silicon, and/or zinc. In still another embodiment of the invention, the copper alloy base metal is a metal strip. In one aspect of this embodiment, the thickness of the copper alloy strip is not more than about 5080 microns. In another aspect of this embodiment, the thickness of the copper alloy strip is less than about 2540 microns. In yet another aspect of this embodiment, the thickness of the copper alloy strip is less than about 1270 microns. In still another aspect of this embodiment, the thickness of the copper alloy strip is less than about 762 microns. In a further aspect of this embodiment, the thickness of the copper alloy strip is about 127-762 microns. In yet a further aspect of this embodiment, the thickness of the copper alloy strip is about 254-762 microns. In still a further aspect of this embodiment, the thickness of the copper alloy strip is about 381-762 microns. In yet another embodiment of the invention, the copper alloy base metal is a metal plate.
In accordance with a further aspect of the invention, the base metal is made of aluminum, aluminum alloys, nickel alloys, tin, titanium, or titanium alloys. xe2x80x9cAluminum alloysxe2x80x9d are used herein include, but are not limited to, alloys including at least about 10 weight percent aluminum. xe2x80x9cNickel alloysxe2x80x9d are used herein include, but are not limited to, alloys including at least about 5 weight percent nickel. In one embodiment of the invention, the base metal is an aluminum metal strip. In another embodiment of the invention, the base metal is a aluminum alloy metal strip. In yet another embodiment of the invention, the base metal is a nickel alloys, tin, titanium, or titanium alloys strip. In still another embodiment of the invention, the base metal is a tin metal strip. In still yet another embodiment of the invention, the base metal is a titanium metal strip. In a further embodiment of the invention, the base metal is a titanium alloy metal strip. In one aspect of these embodiments, the thickness of the aluminum, aluminum alloys, nickel alloys, tin, titanium, or titanium alloys strip is less than about 2540 microns. In another aspect of these embodiments, the thickness of the aluminum, aluminum alloys, nickel alloys, tin, titanium, or titanium alloys strip is less than about 1588 microns. In yet another aspect of these embodiments, the thickness of the aluminum, aluminum alloys, nickel alloys, tin, titanium, or titanium alloys strip is less than about 1270 microns. In still another aspect of these embodiments, the thickness of the aluminum, aluminum alloys, nickel alloys, tin, titanium, or titanium alloys strip is up to about 762 microns. In a further aspect of these embodiments, the thickness of the aluminum, aluminum alloys, nickel alloys, tin, titanium, or titanium alloys strip is about 127-762 microns. In yet a further aspect of these embodiments, the thickness of the aluminum, aluminum alloys, nickel alloys, tin, titanium, or titanium alloys strip is about 240-762 microns. In still a further aspect of these embodiments, the thickness of the aluminum, aluminum alloys, nickel alloys, tin, titanium, or titanium alloys strip is about 381-762 microns. In yet a further embodiment of the invention, the base metal is an aluminum metal plate. In still a further embodiment of the invention, the base metal is a aluminum alloy metal plate. In still yet a further embodiment of the invention, the base metal is a nickel alloy plate. In another embodiment of the invention, the base metal is a tin metal plate. In yet another embodiment of the invention, the base metal is a titanium metal plate. In still another embodiment of the invention, the base metal is a titanium alloy metal plate.
In accordance with a yet further aspect of the invention, the base metal is pretreated prior to applying the metal alloy to the base metal. The pretreatment of the base metal is designed to remove dirt, oil, adhesives, plastic, paper and other foreign substances from the surface of the base metal; to remove oxides and other compounds from the base metal surface; etch the base metal surface; and/or improve the bonding of the metal alloy coating to the surface of the base metal. The pretreatment process may include one or more process steps depending on the surface condition of the base metal. In one embodiment of the invention, the various steps of the pretreatment process for the base metal are similar to the pretreatment process disclosed in U.S. Pat. No. 5,395,702, which is incorporated herein. In another embodiment of the invention, the pretreatment process includes, but is not limited to, an abrasion process; an absorbent process; solvent and/or cleaning solution process; a low oxygen environment process; a rinse process; a pickling process; a chemical activation process; a flux treating process; and/or an intermediate barrier metal layer coating process. In one aspect of this embodiment, each of these pretreatment process can be use singly or in combination with one another. The type and/or number of pretreatment process used generally depends on the type of base metal and/or condition of the base metal surface. The pretreatment process can be applied to a portion of the base metal surface or the complete surface of the base metal.
The abrasion process, absorbent process and/or solvent or cleaning process are designed to remove foreign materials and/or oxides from the base metal surface. In one embodiment of the invention, the abrasion process includes, but is not limited to, the use of brushes, scrappers and the like to mechanically remove oxides and/or foreign material from the surface of the base metal. In another embodiment of the invention, the absorbent process includes, but is not limited to, the use of absorbing materials (i.e. towels, absorbent paper products, sponges, squeegees, etc.) to mechanically remove oxides and/or foreign material from the surface of the base metal. In still another embodiment of the invention, the solvent or cleaning process includes, but is not limited to, the use of water, detergents, abrasives, chemical solvents, and/or chemical cleaners to remove oxides and/or foreign material from the surface of the base metal. The abrasion process, absorbent process, and/or solvent or cleaning process can be use individually or in conjunction with one another to remove foreign materials and/or oxides from the base metal surface.
The low oxygen environment process is designed to inhibit the formation and/or reformation of oxides on the surface of the base metal. The low oxygen environment may take on several forms such as, but not limited to, a low oxygen-containing gas environment and/or a low oxygen-containing liquid environment. Examples of gases used in the low oxygen-containing gas environments include, but are not limited to, nitrogen, hydrocarbons, hydrogen, noble gasses and/or other non-oxidizing gasses. The one or more gases partially or totally shield oxygen and/or other oxidizing elements or compounds from the base metal. In one embodiment of the invention, the low oxygen-containing gas environment includes nitrogen. Examples of liquids used in the low oxygen-containing liquid environment include, but are not limited to, non-oxidizing liquids and/or liquids containing a low dissolved oxygen content. The liquids partially or totally shield oxygen and/or other oxidizing elements or compounds from the base metal. In another embodiment of the invention, the low oxygen-containing liquid environment includes heated water that is at least about 100-110xc2x0 F. In still another embodiment of the invention, the low oxygen-containing environment is applied to the base metal by spraying the low oxygen-containing environment onto the surface of the base metal, partially or totally immersing the base metal in the low oxygen-containing environment, and/or encasing the base metal in the low oxygen-containing environment. In still yet another embodiment of the invention, agitators are used in the low oxygen-containing liquid environment to facilitate in the removal of oxides and/or inhibit oxide formation on the base metal. The agitators can include brushes which contact the base metal.
The rinsed process is designed to remove foreign materials, oxides, pickling solution, deoxidizing agent, fluxes, solvents, and/or cleaning solutions from the surface of the base metal. In one embodiment of the invention, the rinse process includes the use of a rinse solution that includes a low or non-oxidizing liquid. In one aspect of this embodiment, the low or non-oxidizing liquid includes water that is at least about 70xc2x0 F. In another embodiment of the invention, the rinse solution can be applied to the surface of the metal strip by spraying the rinse solution onto the metal strip and/or partially or totally immersing the metal strip in the rinse solution. In yet another embodiment of the invention, the rinse solution is agitated to facilitate in the cleaning of the base metal surface. In still another embodiment of the invention, the rinse solution is recirculated, diluted and/or temperature is maintained during the rinsing process.
The pickling process is designed to remove a very thin surface layer from the base metal. The removal of the thin layer from the base metal results in the partial or total removal of oxides and/or other foreign matter from the base metal surface. The removal of the thin surface layer from the base metal causes slight etching of the base metal surface which results in the formation of microscopic valleys on the base metal surface. These microscopic valleys increase the surface area to which the metal alloy and/or intermediate barrier metal layer can bond thereby facilitating in the formation of a stronger bond between the base metal and the metal alloy and/or intermetallic barrier metal layer. The pickling process includes the use of a pickling solution which can be an acidic or a basic solution. In one embodiment of the invention, the pickling solution is an acidic solution. The acid can be an organic acid, an inorganic acid, or combinations thereof. In one aspect of this embodiment, the inorganic acid used in the pickling solution includes, but are not limited to, hydrobromic acid, hydroiodic acid, choleic acid, perchloric acid, hydrofluoric acid, sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, and/or isobromic acid. In another aspect of this embodiment, the organic acid used in the pickling solution includes, but are not limited to, formic acid, propionic acid, butyric acid, and/or isobutyric acid. In another embodiment of the invention, the pickling solution includes a single acid. Most base metal surfaces can be satisfactorily cleaned or pickled with the use of a single acid. In one aspect of this embodiment, the pickling solution only includes an inorganic acid. In still another embodiment of the invention, the pickling solution includes two or more acids. Some base metals are more difficult to clean or pickle. Stainless steel, as with other metals, is known to have surface oxides that are difficult to remove. When coating stainless steel, it is very desirable to activate (i.e. remove surface oxides) the stainless steel surface so as to form a strong bond and uniformly coat the stainless steel base metal. The chromium in the stainless steel surface reacts with atmospheric oxygen to form a chromium oxide film on the surface of the stainless steel. The chromium oxide film creates an almost impenetrable barrier which protects the iron in the stainless steel from oxidizing. The chromium oxide film also forms a very tight and strong bond with the stainless steel, thus is not easily removable. Although the formation of the chromium oxide film is important in the corrosion-resistant properties of the stainless steel and is intended for commercial stainless steel, the chromium oxide film can interfere with the bonding of the metal alloy coating to the stainless steel surface thereby resulting in weaker bond with the metal alloy coating, thus resulting in flaking of the metal alloy coating. The surface activation of a stainless steel, as with other base metals, is accomplished by removing the oxides on the surface of the base metal. The removal of the chromium oxide film from the stainless steel surface activates the stainless steel surface. Testing of stainless steel has revealed that the removal of chromium oxide film improves the bonding of the metal alloy coating and allows for thick and/or uniform metal alloy coatings to be formed. Oxide removal on other base metals also improves the bonding, coating uniformity and/or coating thickness of the metal alloy coating. Pickling solutions that include two or more acids typically can provide a more rapid oxide removal rate. As can be appreciated, the use of a pickling solution that includes two or more acids is not limited to use on stainless steel or other base metals wherein oxide removal is difficult, but can be used on base metals to increase the rate of cleaning or pickling thereby reducing time for the pickling process. In one aspect of this embodiment, the pickling solution contains a combination of hydrochloric acid and nitric acid. One specific formulation of this dual acid pickling solution is the pickling solution including about 5-25% by volume hydrochloric acid and about 1-15% by volume nitric acid. A more specific formulation of this dual acid pickling solution is the pickling solution including about 5-15% by volume hydrochloric acid and about 1-5% by volume nitric acid. A yet more specific formulation of this dual acid pickling solution is the pickling solution including about 10% by volume hydrochloric acid and about 3% by volume nitric acid. In yet another embodiment of the invention, the temperature of the pickling solution is maintained to obtain the desired activity of the pickling solution. In one aspect of this embodiment, the pickling solution is maintained at a temperature of above about 26xc2x0 C. In another aspect of this embodiment, the pickling solution is maintained at a temperature of about 48-60xc2x0 C. In yet another aspect of this embodiment, the pickling solution is maintained at a temperature of about 53-56xc2x0 C. Higher acid concentrations and/or higher acid temperatures will typically increase the activity and aggressiveness of the pickling solution. In yet another embodiment of the invention, the pickling solution is agitated to prevent or inhibit the pickling solution from stagnating, varying in concentration, varying in temperature, and/or to remove gas pockets which form on the base metal surface. In one aspect of this embodiment, the pickling solution is at least partially agitated by placing agitators in a pickling tank and/or by recirculating the pickling solution in a pickling tank. Typically, agitation brushes in the pickling tank contacts base metal as it passes through the pickling tank to facilitate in oxide removal and cleaning of the base metal surface. In another embodiment of the invention, the base metal is exposed to the pickling solution for a sufficient time to properly clean and/or pickle the surface of the base metal. In one aspect of this embodiment, the total time for pickling the base metal is less than about 10 minutes. In another aspect of this embodiment, the total time for pickling the base metal is less than about two minutes. In still another aspect of this embodiment, the total time for pickling the base metal is less than about one minute. In still yet another aspect of this embodiment, the total time for pickling the base metal is about 5-60 seconds. In a further aspect of this embodiment, the total time for pickling the base metal is about 10-20 seconds. In still another embodiment, the pickling solution is applied to the base metal by spray jets. In yet another embodiment, the base metal is partially or fully immersed in the pickling solution contained in a pickling tank.
The chemical activation process is designed to remove oxides and/or foreign material from the base metal surface. In one embodiment of the invention, the chemical activation process includes subjecting the base metal surface to a deoxidizing agent. Various types of deoxidizing agents may be used. In another embodiment of the invention, the deoxidizing agent includes zinc chloride. In one aspect of this embodiment, the deoxidizing agent includes at least about 1% by volume zinc chloride. In another aspect of this embodiment, the deoxidizing agent includes at least about 5% by volume zinc chloride. The zinc chloride removes oxides and foreign materials from the base metal surface and/or provides a protective coating which inhibits oxide formation on the base metal surface. In still another embodiment of the invention, the temperature of the zinc chloride solution is at least about ambient temperature (about 15-32xc2x0 C.). In yet another embodiment, the deoxidizing solution is agitated to maintain a uniform solution concentration and/or temperature. In one aspect of this embodiment, the agitators include brushes which contact the base metal. In still yet another embodiment of the invention, small amounts of acid are added to the deoxidizing solution to enhance oxide removal. In one aspect of this embodiment, hydrochloric acid is added to the deoxidizing solution. In this aspect, one formulation of the deoxidizing solution includes about 1-50% by volume zinc chloride and about 0.5-15% by volume hydrochloric acid. In this aspect, another formulation of the deoxidizing solution includes about 5-50% by volume zinc chloride and about 1-15% by volume hydrochloric acid. In a further embodiment of the invention, the base metal is subjected to the deoxidizing solution for less than about 10 minutes. In one aspect of this embodiment, the base metal is subjected to the deoxidizing solution for up to about one minute. In still a further embodiment, the deoxidizing solution is applied to the base metal by spray jets. In yet a further embodiment, the base metal is partially or fully immersed in the deoxidizing solution contained in a deoxidizing tank.
The intermediate barrier metal process is designed to coat one or more surface areas of the base metal with a thin metal coating. The intermediate metal barrier is applied to part of or the complete surface of the base metal by a plating process, a plating and subsequent flow heating process, a metal spraying process, a coating roller process, and/or immersion process in molten metal prior to applying the metal alloy coating to the base metal surface. The intermediate barrier metal typically provides additional corrosion resistance to the base metal in many types of corrosive environments. In marine environments where the coated base metal is exposed to salt and/or halogens (i.e. chlorine, fluorine, etc.), the use of an intermediate barrier metal can significantly extend the life of the coated base metal. The use of an intermediate barrier metal can also enhance the bonding of the metal alloy coating to the base metal. Some base metals such as, but not limited to, stainless steel, form a weaker bond with certain formulations of the metal alloy. The application of an intermediate barrier metal on part of or the complete surface of the base metal can, in many instances, improve the strength of the bond of the metal alloy coating to the base metal. The intermediate barrier metal is typically tin, nickel, copper, and/or chromium. Other metals can be used for the intermediate barrier metal, such as, but not limited to, aluminum, cobalt, molybdenum, Snxe2x80x94Ni, Fexe2x80x94Ni, and/or zinc. Typically, one intermediate barrier metal is formed on the surface of the base metal; however, more than one layer of one or more barrier metals can be applied to the surface of the base metal to form a thicker intermediate barrier metal layer, alter the composition of the intermediate barrier metal layer, alter the composition of the heat created intermetallic layer if formed, and/or improve the bonding of the metal alloy coating to the intermediate barrier metal layer and/or base metal. In one embodiment of the invention, the intermediate barrier metal includes nickel. Typically, the nickel is flashed or plated to the base metal surface. The nickling including intermediate barrier metal layer improves corrosion-resistance of the base metal and/or metal alloy, especially against halogen containing compounds which can penetrate the metal alloy coating and attack and oxidize the surface of the base metal thereby weakening the bond between the base metal and the metal alloy coating. The nickel including intermediate barrier metal layer has also been found to provide a formidable barrier to alcohols and/or various type of petroleum products. The metal alloy coating and nickel including intermediate barrier metal effectively complement one another to provide superior corrosion resistance. An intermediate barrier metal layer which includes nickel also improves the bonding of the metal alloy coating to the base metal. The bond between the metal alloy coating and the nickel layer is surprisingly strong and durable and thereby inhibits the metal alloy coating from flaking. An intermediate barrier metal layer which includes nickel also inhibits the formation of a thick zinc layer in the intermetallic layer, when zinc is included in the metal alloy. In another embodiment of the invention, the intermediate barrier metal includes tin, chromium and/or copper. An intermediate barrier metal layer which includes tin, chromium and/or copper improves the bonding of the metal alloy coating to the base metal. The tin, chromium and/or copper in the intermediate barrier metal also has been found to inhibit adverse zinc intermetallic layer growth from the zinc in a zinc containing metal alloy. A thick zinc layer can cause poor coating quality or cracking of the coating during forming and bending, give rise to localized corrosion, and/or adversely affect performance of the coated strip in particular applications. When copper is included in the intermediate barrier metal, the copper is typically plated onto the surface of the base metal. The plated copper layer can be, but is not limited to being, formed by passing the base metal through an electroplating process or by adding copper sulfate to a pickling solution and pickling the coated base metal. A copper containing intermediate barrier metal layer also enhances the corrosion-resistant properties of the heat created intermetallic layer, improves the bonding of the metal alloy to the base metal, and/or improve the corrosion resistance of the metal alloy and/or base metal. When tin in included in the intermediate barrier metal, the tin is typically coated onto the base metal by immersion in molten metal, plating and/or metal spraying. A tin containing intermediate barrier metal advantageously changes the composition of the heat created intermetallic layer to form a highly corrosion-resistant heat created intermetallic layer, improves the bonding of the metal alloy to the base metal, and/or improves the corrosion-resistance of the metal alloy and/or base metal. When chromium is included in the intermediate barrier metal, the chromium is typically plated onto the surface of the base metal. A chromium containing intermediate barrier metal layer advantageously changes the composition of the heat created intermetallic layer to form a highly corrosion-resistant heat created intermetallic layer, improves the bonding of the metal alloy, and/or improves the corrosion resistance of the metal alloy and/or base metal. In still another embodiment of the invention, the intermediate barrier metal includes aluminum, cobalt, molybdenum, Snxe2x80x94Ni, Fexe2x80x94Ni, and/or zinc. The aluminum, cobalt, molybdenum, Snxe2x80x94Ni, Fexe2x80x94Ni, and/or zinc are typically plated to the base metal by a plating process. An intermediate barrier metal layer which includes aluminum, cobalt, molybdenum, Snxe2x80x94Ni, Fexe2x80x94Ni, and/or zinc improves the bonding of the corrosion resistant metal alloy coating to the base metal, enhances the corrosion-resistant properties of the heat created intermetallic layer, and/or improve the corrosion-resistance of the metal alloy and/or base metal. In yet another embodiment of the invention, the thickness of the intermediate barrier metal layer is at least about 0.3 micron. In one aspect of this embodiment, the thickness of the intermediate barrier metal layer is at least about 1 micron. In another aspect of this embodiment, the thickness of the intermediate barrier metal layer is less than about 500 microns. In yet another aspect of this embodiment, the thickness of the intermediate barrier metal layer is less than about 250 microns. In still another specific aspect of this embodiment, the thickness of the intermediate barrier metal layer is less than about 50 microns. In still yet another aspect of this embodiment, the thickness of the intermediate barrier metal layer is less than about 20 microns. In a further aspect of this embodiment, the thickness of the intermediate barrier metal layer is about 1-10 microns. In yet a further aspect of this embodiment, the thickness of the intermediate barrier metal layer is about 1-3 microns. In accordance with still yet another embodiment of the invention, the intermediate barrier metal layer is pre-heated and/or flow heated prior to applying the metal alloy coating to the base metal. The heating of the intermediate barrier metal layer to a sufficient temperature for a sufficient amount of time causes a heat created intermetallic layer to form between the intermediate barrier metal layer and the base metal. A heat created intermetallic layer is formed without the use of a subsequent heating step when the intermediate barrier metal is applied to the base metal by a metal spraying process, a coating roller process, and/or an immersion process. The temperature of the intermediate barrier metal in the molten state causes a heat created intermetallic layer to form between the intermediate barrier metal and the base metal when the molten intermediate barrier metal contacts the surface of the base metal. When the intermediate barrier metal is applied by a plating or pickling process, a subsequent heating step is needed to form the heat created intermetallic layer between the intermediate barrier metal and the base metal. A xe2x80x9cheat created intermetallic layerxe2x80x9d is defined herein as a metal layer formed by heat wherein the metal layer is a mixture of at least the primary surface components of the base metal and components of a coated metal layer (i.e. intermediate barrier metal and/or metal alloy coating). The application of heat to the base metal and a coated metal layer causes the surface of the base metal to soften and/or melt and to combine with a portion of the soften or melted coated metal layer. In many instances, the formation of a heat created intermetallic layer results in improved bonding of the coated metal to the base metal, and/or improves the corrosion-resistance of the base metal and/or coated metal layer. In one aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the intermediate barrier metal is at least about 0.1 micron. In another aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the intermediate barrier metal is at least about 0.3 micron. In still another aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the intermediate barrier metal is at least about 0.5 micron. In still another aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the intermediate barrier metal is at least about 1 micron. In yet another aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the intermediate barrier metal is less than about 100 microns. In still yet another aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the intermediate barrier metal is less than about 50 microns. In a further aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the intermediate barrier metal is less than about 25 microns. In yet a further aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the intermediate barrier metal is less than about 20 microns. In still a further aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the intermediate barrier metal is less than about 10 microns. In still yet a further aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the intermediate barrier metal is about 1-10 microns. In still yet a further aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the intermediate barrier metal is about 1-5 microns. In still yet even a further aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the intermediate barrier metal is about 1-3 microns. Typically the formation of a heat created intermetallic layer takes at least a couple seconds to form. In one embodiment of the present invention, the base metal is exposed to heat for at least about 2 seconds to form the heat created intermetallic layer between the base metal and the intermediate barrier metal. The time period of heat exposure for an intermediate barrier metal layer applied by a plating and/or a pickling process is the time the intermediate barrier metal is exposed to heat after the plating and/or pickling process. The time period for heat exposure for an intermediate barrier metal layer applied by metal spraying, coating rollers, and/or immersion in molten metal includes the time of applying the intermediate barrier metal to the base metal and the time the intermediate barrier metal is exposed to heat after the metal spraying, coating rollers, and/or immersion in molten metal process. Typically, the time of total heat exposure is less than about four hours; however, greater heat exposure times can be used. In one aspect of this embodiment, the total time period of heat exposure to an intermediate barrier metal layer applied to the base metal to form an intermetallic layer between the base metal and the intermediate barrier metal layer is less than about 20 minutes. In another aspect of this embodiment, the total time period of heat exposure to an intermediate barrier metal layer applied to the base metal to form an intermetallic layer between the base metal and the intermediate barrier metal layer is less than about 10 minutes. In yet another aspect of this embodiment, the total time period of heat exposure to an intermediate barrier metal layer applied to the base metal to form an intermetallic layer between the base metal and the intermediate barrier metal layer is less than about 5 minutes. In still another aspect of this embodiment, the total time period of heat exposure to an intermediate barrier metal layer applied to the base metal to form an intermetallic layer between the base metal and the intermediate barrier metal layer is about 0.033-2 minutes. When heat is applied to the coated base metal to form or further form the heat created intermetallic layer between the base metal and intermediate metal barrier layer, the heat typically is applied by, but not limited to, an oven and/or furnace, induction heating coils, lasers, heat exchanger, and/or radiation. As can be appreciated, the flow heating of the plated intermediated barrier layer can also function as a pre-heat process for the base metal. Alternatively, or in addition to, the heat can be supplied by coating the base metal and the intermediated metal barrier layer with a metal alloy by a hot-dip process. The heat from the hot-dip process causes the formation of the heat created intermetallic layer. In still another embodiment of the invention, the application of the intermediate barrier metal layer on the surface of the base metal is a partial or complete pretreatment process for the surface of the base metal prior to applying the metal alloy coating to the base metal. The application of the an intermediate barrier metal to the surface of the base metal forms a clean metal surface on the base metal surface. Due to this clean metal surface, the application of the an intermediate barrier metal to the surface of the base metal can function as the sole pretreatment process for the surface of the base metal. As can be appreciated, the surface of the base metal can be pretreated with other pretreatment process prior to applying the intermediate barrier metal layer and/or pretreated with other pretreatment process subsequent to applying the intermediate barrier metal layer.
In accordance with another aspect of the invention, metal alloy coating is coated on the base metal by a plating process or by a hot dip process. The coating process for the metal alloy coating can be by a batch or continuous process. As defined herein, a xe2x80x9chot dip processxe2x80x9d for the metal alloy is any process that coats the metal alloy coating on the base metal and causes the formation of a heat created intermetallic layer between the base metal and the metal alloy coating. Examples of a hot dip process include, but are not limited to, 1) plating a metal alloy coating partially or totally on the base metal and subsequently heating the plated layer until a heat created intermetallic layer forms between the plated layer and the base metal, 2) plating a metal alloy partially or totally on the base metal and subsequent partial or total immersion of the base metal in a molten bath of metal alloy for a sufficient period of time to partially or totally coat the base metal and to form a heat created intermetallic layer between the coated metal alloy layer and the base metal, 3) plating a metal alloy partially or totally on the base metal and subsequent spray coating molten metal alloy onto the base metal to partially or totally coating the base metal wherein the base metal is spray coated for a sufficient period of time to form a heat created intermetallic layer between the coated metal layer and base metal, 4) plating a metal alloy partially or totally on the base metal and subsequent partial or total immersion of the base metal in a molten bath of metal alloy and spray coating molten metal alloy onto the base metal to partially or totally coat the base metal wherein the base metal is spray coated and immersed for a sufficient period of time to form a heat created intermetallic layer between the coated metal layer and base metal, 5) partial or total immersion of the base metal in a molten bath of metal alloy for a sufficient period of time to partially or totally coat the base metal and to form a heat created intermetallic layer between the coated metal layer and the base metal, 6) partial or total immersion of the base metal in a molten bath of metal alloy for a sufficient period of time to partially or totally coat the base metal and spray coating molten metal alloy onto the base metal to partially or totally coat the base metal wherein the base metal is immersed and sprayed for a sufficient period of time to form a heat created intermetallic layer between the coated metal layer and base metal, 7) spray coating the base metal with molten metal alloy to partially or totally coat the base metal for a sufficient period of time to form a heat created intermetallic layer between the coated metal layer and the base metal, 8) plating and subsequent heating and subsequent immersion in molten metal alloy coating and/or spray coating molten metal alloy coating, 9) plating and subsequent heating and subsequent immersion in molten metal alloy coating and/or spray coating molten metal alloy coating and subsequent heating after immersion in molten metal alloy coating and/or spray coating molten metal alloy coating, 10) immersion in molten metal alloy coating and subsequent heating, 11) immersion in molten metal alloy coating and spray coating molten metal alloy coating and subsequent heating after immersion and spray coating, 12) spray coating molten metal alloy coating and subsequent heating after spray coating, 13) coating molten metal alloy by coating rollers, 14) coating molten metal alloy by coating rollers and spray coating, 15) immersion in molten metal alloy and coating molten metal alloy by coating rollers, 16) plating and coating molten metal alloy by coating rollers, and 17) coating molten metal alloy by coating rollers and subsequent heating. As can be appreciated, many other hot dip coating combinations can be used. As further can be appreciated, the base metal can be coated a multiple of times by various types of coated processes. When heat is subsequently applied to the coated base metal to form or further form the heat created intermetallic layer between the base metal and the metal alloy coating, the heat typically is applied by, but not limited by, an oven and/or furnace, induction heating coils, lasers, heat exchanger, and/or radiation. In one embodiment of the invention, the thickness of the heat created intermetallic layer is at least about 0.3 micron. In still another aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the metal alloy coating is at least about 1 micron. In yet another aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the metal alloy coating is less than about 100 microns. In still yet another aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the metal alloy coating is less than about 50 microns. In a further aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the metal alloy coating is less than about 25 microns. In yet a further aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the metal alloy coating is less than about 20 microns. In still a further aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the metal alloy coating is less than about 10 microns. In still yet a further aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the metal alloy coating is about 1-5 microns. In still yet even a further aspect of this embodiment, the thickness of the heat created intermetallic layer formed between the base metal and the metal alloy coating is about 1-3 microns. Typically, the formation of a heat created intermetallic layer takes at least a couple seconds to form. In one embodiment of the invention, the base metal is exposed to heat for at least 2 seconds to form the heat created intermetallic layer between the base metal and the metal alloy coating. The time period of heat exposure of a metal alloy coating layer applied by a plating process is the time the metal alloy coating is exposed to heat after the plating process. The time period for heat exposure for a metal alloy coating layer applied by metal spraying, coating rollers and/or immersion in molten metal includes the time of applying the metal alloy coating to the base metal and the time the metal alloy coating is exposed to heat after the metal spraying, coating rollers, and/or immersion in molten metal process. In one aspect of this embodiment, the total time period of heat exposure to a metal alloy coating layer applied to the base metal to form an intermetallic layer between the base metal and the metal alloy coating layer is less than about 3 hours. In another aspect of this embodiment, the total time period of heat exposure to a metal alloy coating layer applied to the base metal to form an intermetallic layer between the base metal and the metal alloy coating layer is less than about 4 hours. In still another aspect of this embodiment, the total time period of heat exposure to a metal alloy coating layer applied to the base metal to form an intermetallic layer between the base metal and the metal alloy coating layer is less than about 2 hours. In yet another aspect of this embodiment, the total time period of heat exposure to a metal alloy coating layer applied to the base metal to form an intermetallic layer between the base metal and the metal alloy coating layer is less than about 1 hour. In still yet another aspect of this embodiment, the total time period of heat exposure to a metal alloy coating layer applied to the base metal to form an intermetallic layer between the base metal and the metal alloy coating layer is less than about 30 minutes. In a further aspect of this embodiment, the total time period of heat exposure to a metal alloy coating layer applied to the base metal to form an intermetallic layer between the base metal and the metal alloy coating layer is less than about 20 minutes. In yet further aspect of this embodiment, the total time period of heat exposure to a metal alloy coating layer applied to the base metal to form an intermetallic layer between the base metal and the metal alloy coating layer is less than about 10 minutes. In still a further another aspect of this embodiment, the total time period of heat exposure to a metal alloy coating layer applied to the base metal to form an intermetallic layer between the base metal and the metal alloy coating layer is less than about 5 minutes. In still yet further aspect of this embodiment, the total time period of heat exposure to a metal alloy coating layer applied to the base metal to form an intermetallic layer between the base metal and the metal alloy coating layer is about 0.033-2 minutes. In still a further aspect of this embodiment, the total time period of heat exposure to a metal alloy coating layer applied to the base metal to form an intermetallic layer between the base metal and the metal alloy coating layer is about 0.033-0.5 minutes. In yet a further aspect of this embodiment, the total time period of heat exposure to a metal alloy coating layer applied to the base metal to form an intermetallic layer between the base metal and the metal alloy coating layer is about 0.083-0.5 minutes.
The metal alloy coating formed on the surface of the base metal by a batch coating process or by a continuous coating process can result in different types of coatings. These differences can include, but are not limited to, the following:
a) Uniformity of coating (weight and thickness)
b) Surface appearance
c) Smoothness
d) Texture control
e) Control of intermetallic phases (growth and uniformity)
A base metal coated in a continuous coating process typically produces a coated base metal having superior uniformity of coating (weight and thickness), superior metallographic structure, superior surface appearance, superior smoothness, superior spangle size, and fewer surface defects. Furthermore, the composition of the heat created intermetallic layer is typically superior as compared to a base metal coated in a batch coating process. In addition to surface appearance and uniformity of thickness, the formability of the coated base metal is generally better due to a more uniform coating thickness on the surface of the base metal. In general, thicker coatings provide greater corrosion protection, whereas thinner coatings tend to give better formability and weldability. Thinner coatings with uniformity of thickness can be better formed by a continuous coating process.
In still another aspect of the invention, the metal alloy coating is applied to the surface of the base metal, the surface of the intermediate barrier metal layer, and/or an existing metal alloy coating by a plating process. When a plating process is used, a heat created intermetallic layer is not formed between the metal alloy coating and the surface of the base metal, the surface of the intermediate barrier metal layer, and/or a previously applied metal alloy coating. Typically, the plating process is carried out by standard plating processes, thus a detailed description of a plating process is not described herein. The complete or partial surface of the base metal, the surface of the intermediate barrier metal layer, and/or surface of a previously applied metal alloy can be coated by the plating process. The plating of the components of the corrosion resistant metal alloy can be accomplished at the same time or in subsequent steps. For instance, a corrosion resistant tin metal alloy which includes lead can be plated by a) simultaneously plating the tin and lead onto the surface of the base metal, the surface of the intermediate barrier metal layer, and/or metal alloy coating, b) first plating the tin on the surface of the base metal, the surface of the intermediate barrier metal layer and/or metal alloy coating, and subsequently plating the lead on the surface of the base metal, the surface of the intermediate barrier metal layer, and/or metal alloy coating, or c) first plating the lead on the surface of the base metal, the surface of the intermediate barrier metal layer, and/or metal alloy coating, and subsequently plating the tin on the surface of the base metal, the surface of the intermediate barrier metal layer, and/or metal alloy coating. Similarly, a corrosion resistant tin and zinc metal alloy which includes antimony can be plated by a) simultaneously plating the tin, zinc and antimony onto the surface of the base metal, the surface of the intermediate barrier metal layer, and/or metal alloy coating, b) first plating the tin on the surface of the base metal, the surface of the intermediate barrier metal layer, and/or metal alloy coating, then plating the zinc on the surface of the base metal, the surface of the intermediate barrier metal layer, and/or metal alloy coating, and subsequently plating the antimony on the surface of the base metal, the surface of the intermediate barrier, metal layer, and/or metal alloy coating, c) first plating the zinc on the surface of the base metal, the surface of the intermediate barrier metal layer, and/or metal alloy coating, then plating the tin on the surface of the base metal, the surface of the intermediate barrier metal layer, and/or metal alloy coating, and subsequently plating the antimony on the surface of the base metal, the surface of the intermediate barrier metal layer, and/or metal alloy coating, d) first plating the antimony on the surface of the base metal, the surface of the intermediate barrier metal layer, and/or metal alloy coating, and subsequently simultaneously plating tin and zinc on the surface of the base metal, the surface of the intermediate barrier metal layer, and/or metal alloy coating, etc. In one embodiment of the invention, a tin metal alloy is plated on the surface of the base metal. In one specific aspect of this embodiment, the plating process includes the plating of tin in an electrolytic solution containing stannous tin and an acid. In another embodiment of the invention, a tin and zinc metal alloy is plated on the surface of the base metal. In one specific aspect of this embodiment, the plating process includes the plating of tin and zinc in an electrolytic solution containing stannous tin, zinc and an acid.
In yet another aspect of the invention, the metal alloy coating is applied to the surface of the base metal, the surface of the intermediate barrier metal layer, and/or previously applied metal alloy coating by a hot dip process that includes plating and subsequent heating of the plated metal alloy. The metal alloy is plated onto the surface of the base metal, the surface of the intermediate barrier metal layer, and/or a previously applied metal alloy coating by a plating process that is the same as or similar to the plating process described above. After the metal alloy is plated onto the surface of the base metal, the surface of the intermediate barrier metal layer, and/or previously applied metal alloy coating, the plated metal alloy coating is subjected to heat for a sufficient period of time to form a heat created intermetallic layer between the plated metal alloy coating and the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating. If one or more of the components of the corrosion resistant metal alloy coating were plated by a separate plating process, the plated metal components of the metal alloy coating can be subjected to heat after one or more of the plating processes, or after all the components of the metal alloy coating have been coated onto the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating. The heating of the plated metal alloy coating causes at least a portion of the alloy to enter a molten state and to form an at least partially uniform and substantially level coating layer. The heating of the plated metal alloy coating also facilitates in the reduction and/or elimination of pin holes in the metal alloy coating which may have formed during the plating process. The time period selected for flow heating the plated metal alloy coating depends on the time necessary to soften and/or melt the desired amount of tin in the tin metal alloy coating or tin and zinc in the tin and zinc metal alloy coating to form the desired thickness of the heat created intermetallic layer. When one or more of the components of the corrosion resistant metal alloy coating are plated by separate plating process, the plated metal components of the metal alloy coating are subjected to heat for a sufficient period of time to at least partially alloy together the components of the metal alloy coating. The heating process for the plate metal alloy can be by a batch or by a continuous process. In one embodiment of the invention, the plated metal alloy coating is exposed to heat by the application of another molten metal alloy coating onto the surface of the plated metal alloy coating. The heat of the molten metal alloy upon contact with the plated metal alloy causes the components of the plated metal alloy coating to at least partially alloy together and/or form the desired thickness of the heat created intermetallic layer between the plated metal alloy coating and the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating. In one aspect of this embodiment, a molten metal alloy is applied by immersion is coated onto the surface of the plated metal alloy coating. In another aspect of this embodiment, a molten metal alloy is applied by coating rollers is coated onto the surface of the plated metal alloy coating. In still another aspect of this embodiment, a molten metal alloy is applied by spray coating is coated onto the surface of the plated metal alloy coating. In another embodiment of the invention, the plated metal alloy coating is exposed to an external heat source for a time period and temperature sufficient to at least partially alloy together the components of the plated metal alloy coating and/or form the desired thickness of the heat created intermetallic layer between the plated metal alloy coating and the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating. The plated metal alloy coating is typically exposed to heat through the use of a convection oven, a furnace, heated fluids, flames, induction heating, lasers, hot gasses, radiation, and the like. In one aspect of this embodiment, the temperature the plated metal alloy is exposed to is at least about 200xc2x0 C. In another aspect of this embodiment, the temperature the plated metal alloy is exposed to is less than about 2000xc2x0 C. In still another aspect of this embodiment, the temperature the plated metal alloy is exposed to is less than about 1000xc2x0 C. In yet another aspect of this embodiment, the temperature the plated metal alloy is exposed to is less than 500xc2x0 C.
In accordance with still yet another aspect of the invention, the corrosion resistant metal alloy is coated onto the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating by immersion into molten corrosion resistant metal alloy. In one embodiment of the invention, the molten corrosion resistant metal alloy is maintained at a temperature of at least about 232xc2x0 C. (449xc2x0 F.). In one aspect of this embodiment, the molten corrosion resistant metal alloy is maintained at a temperature of at least about 2-30xc2x0 C. above the melting point of the corrosion resistant metal alloy. In another embodiment of the invention, the residence time of the base metal in the molten corrosion resistant alloy is selected to form the desired heat created intermetallic layer between the corrosion resistant alloy metal coating and the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating. In one aspect of this embodiment, the residence time of the base metal in the molten metal alloy is at least about 0.033-0.083 minutes. In another aspect of this embodiment, the residence time of the base metal in the molten metal alloy is less than about 10 minutes. In still another aspect of this embodiment, the residence time of the base metal in the molten metal alloy is less than about two minutes. In yet another aspect of this embodiment, the residence time of the base metal in the molten metal alloy is less than about one minute. In still yet another aspect of this embodiment, the residence time of the base metal in the molten metal alloy is about 0.083-0.5 minutes.
In accordance with another aspect of the invention, the hot dip coating of the base metal by immersion in molten metal alloy includes the use of a flux box. The flux box is designed to receive the base metal prior to the base metal passing into the molten metal alloy. The flux solution in the flux box is formulated to remove residual oxides from the base metal surface, shield the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating from oxygen until the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating base metal is coated with the molten metal alloy, inhibit the formation of viscous oxides at the point where the base metal enters the molten metal alloy, and/or inhibits dross formation on the base metal. The exposure of the base metal to the flux solution is the last pretreatment process of the base metal prior to being coated by immersion in molten metal alloy. In one embodiment of the invention, the flux box contains a flux solution which has a lower specific gravity than the molten metal alloy, thus the flux solution floats on the surface of the molten alloy. In another embodiment of the invention, the flux solution includes a zinc chloride solution. In one aspect of this embodiment, the flux solution includes ammonium chloride. In another aspect of this embodiment, the flux solution includes about 20-75% by volume zinc chloride. In yet another aspect of this embodiment, the flux solution includes zinc chloride and ammonium chloride. In still yet another aspect of this embodiment, the flux solution includes about 20-75% by volume zinc chloride and up to about 40% by volume ammonium chloride. In a further aspect of this embodiment, the flux solution includes about 30-60% by volume zinc chloride and up to about 1-20% by volume ammonium chloride. In yet a further aspect of this embodiment, the flux solution includes about 50% by volume zinc chloride and about 8% by volume ammonium chloride.
In accordance with still another aspect of the invention, the hot dip process of coating the base metal is by immersion in a molten metal alloy includes a melting pot for heating the molten metal alloy. In one embodiment of the invention, the melting pot is heated by heating coils, heating rods, gas jets, induction heating, lasers, radiation, etc. In one aspect of this embodiment, the melting pot is heated by at least one gas jet directed toward at least one side of the melting pot. In another aspect of this embodiment, heating coils and heating rods are used to heat the metal alloy directly in the melting pot. In still another aspect of this embodiment, gas jets are used heat the molten metal alloy in the melting pot.
In accordance with a further aspect of the invention, the hot dip process of coating the base metal by immersion in molten metal alloy includes the use of a protective material on the surface of the molten metal alloy in the melting pot. The protective material is formulated to at least partially shield the molten metal alloy from the atmosphere thereby preventing or inhibiting oxide formation on the surface of the molten metal alloy, and/or preventing or inhibiting dross formation on the coated base metal as the coated base metal enters and/or exits from the melting pot. In one embodiment of the invention, the protective material has a specific gravity which is less than the specific gravity of the molten metal alloy so that the protective material at least partially floats on the surface of the molten metal alloy. In another embodiment of the invention, the protective material includes an oil. In one aspect of this embodiment, the protective material includes palm oil. When the protective material is palm oil, the melting point of the metal alloy should be below about 344xc2x0 C., the degrading point of palm oil. For metal alloys having a higher melting point, other oils, fluxes, or other materials and/or special cooling processes for the protective material are employed when a protective material is used. In still another embodiment, the protective material facilitates in forming a smooth and uniform coating on the surface of the base metal.
In accordance with another aspect of the invention, the thickness of the metal alloy coating by immersion in molten metal alloy is at least partially regulated by the residence time of the base metal in the molten metal alloy, the temperature of the molten metal alloy in the melting pot, and/or the speed at which the base metal moves through the molten metal alloy. In one embodiment of the invention, the base metal is maintained at a substantially constant speed through the molten metal alloy. The substantially uniform speed results in a substantially uniform growth of the heat created intermetallic layer between the metal alloy and the base metal, a substantially smooth coating of metal alloy, and/or a substantially constant metal alloy coating thickness. As the base metal passes through the molten metal alloy at a substantially constant speed, the metal alloy adheres to the moving base metal and shears a portion of the metal alloy coating from the moving base metal. The shearing effect results from the viscosity of the molten alloy and the speed of the moving base metal. For a given speed and metal alloy viscosity, a certain thickness of metal alloy will be applied to the base metal over a given time. The shearing effect results in a substantially uniform coating, excellent surface appearance, excellent smoothness, excellent texture control and a substantially uniform heat created intermetallic layer. In another embodiment of the invention, the base metal is coated by moving the base metal through the molten metal alloy in the melting pot at a relatively constant speed of about 1-400 ft/min. In one aspect of this embodiment, the base metal is moved through the molten metal alloy in the melting pot at a relatively constant speed of about 50-250 ft/min.
In accordance with still another aspect of the invention, the corrosion resistant metal alloy is coated onto the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating by a coating roller process. Molten metal alloy on the coating rollers is applied to the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating by a coating roller process as the base metal passes by or between one or more coating rollers. The coating rollers form a smooth and/or uniform metal alloy coating layer on the base metal. The coating rollers press against and coat the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating and fill pin holes or uncoated surfaces on the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating by a coating roller process. The coating rollers also control the thickness of the metal alloy coating onto the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating by a coating roller process. In one embodiment of the invention, the coating rollers are used in conjunction with an immersion process and/or metal spray process. In another embodiment, the coating rollers are spaced apart a sufficient distance so that the base metal can pass between the coating rollers. As the base metal basses between one or more sets of coating rollers, the coating rollers maintain a desired coating thickness of the metal alloy on the base metal, remove excess metal alloy from the base metal, and/or coat any non-coated regions on the surface of the base metal. In one aspect of this embodiment, the coating thickness of the metal alloy is selected to ensure that essentially no uncoated regions exist on the surface of the base metal. Typically, the thickness of the metal alloy on the surface of base metal is at least about 1 micron, and generally at least about 2.5 microns, more generally about 7 to 2550 microns, and even more generally about 7-1270 microns. In another aspect of this embodiment, the coating thickness of the metal alloy is selected to ensure the coated metal alloy has essentially no pin holes, and/or does not shear when formed into various products. A metal alloy coating thickness of about 25-51 microns forms a coating that has few, if any, pin holes, provides greater elongation characteristics, and resist shearing when formed into various shaped articles. In still another aspect of this embodiment, the thickness of the metal alloy is selected for use in certain types of environments in which the coated base metal is to be used. A metal alloy coating thickness of about 25-51 microns forms a coating that significantly reduces the corrosion of the base metal in virtually all types of environments. Metal alloy coating thicknesses greater than about 51 microns are typically used in harsh environments to provide added corrosion protection. In another embodiment of the invention, the molten metal alloy is maintained at a temperature at least about 2-30xc2x0 C. above the melting point of the metal alloy, while the metal alloy is on the coating rollers. In another embodiment of the invention, the coating processes includes at least one set of coating rollers that partially or fully coat the surface of the base metal as the base metal passes the coating rollers. In another embodiment of the invention, one or more coating rollers are at least partially immersed in molten metal alloy during the coating process. In one aspect of this embodiment, the coating process is used in conjunction with an immersion coating process and one or more of the coating rollers are at least partially immersed in molten metal alloy in the melting pot. In another aspect of this embodiment, one or more of the coating rollers are at least partially immersed in a protective material in the melting pot. In yet another embodiment of the invention, one or more coating rollers are positioned above the molten metal allot in the melting pot when the coating rollers are used in conjunction with an immersion coating process. In still another embodiment of the invention, one or more coating rollers are at least partially coated with molten metal alloy by one or more spray jets that direct molten metal alloy on to the one or more coating rollers. The one or more spray jets direct the molten metal alloy on to the surface of the coating rollers as the base metal passes by or between the coating rollers thereby resulting in the base metal being partially or completely coated with the metal alloy. In still another embodiment of the invention, one or more coating rollers includes an internal cavity in which molten metal alloy is directed into and then directed onto the surface of the coating roller to direct the molten metal alloy on to the surface of the coating rollers as the base metal passes by or between the coating rollers. In still another embodiment of the invention, the time period the base metal is exposed to each coating roller is a relatively short time. The time period is dependant on the speed of the base metal and the size of the coating rollers. Typically, the base metal is exposed to the coating rollers for at least about 0.3 seconds and generally about 0.5-30 seconds. In a further embodiment, one or more coating rollers include one or more grooves. The one or more grooves are designed to facilitate in maintaining the molten metal alloy on the coating roller during the coating process.
In accordance with yet another aspect of the present invention, the corrosion resistant metal alloy is coated onto the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating by a spray coating process. Molten metal alloy is sprayed onto the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating by one or more spray jets. The spray jets spray molten metal alloy onto the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating to at least partially coat the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating, and/or ensure that a uniform and/or continuous coating is applied on the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating. The speed and time the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy is in contact with the molten metal is controlled so that the desired coating thickness and desired thickness of the heat created intermetallic layer is obtained. In one embodiment of the invention, the spray jets are used in conjunction with coating rollers and/or an immersion process. In one aspect of this embodiment, the spray jets at least partially direct molten metal alloy onto the coating rollers and/or onto the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating during the coating process. In another embodiment of the invention, this molten metal alloy is maintained at a temperature of at least about 2-30xc2x0 C. above the melting point of the metal alloy as the metal alloy is sprayed from the one or more spray jets. In yet another embodiment of the invention, the base metal passes by or between one or more metal spray jets during the coating process to partially or completely coat the surface of the base metal. In another embodiment of the invention, the base metal is exposed to the molten metal alloy from the one or more metal spray jets for a sufficient time to partially or fully coat the surface of the base metal. The time the base metal is exposed to the molten metal alloy from the metal spray jets is dependent on the speed of the moving base metal. Typically, the base metal is exposed to the molten metal alloy from the metal spray jets for at least about 0.3 seconds, generally about 0.5-60 seconds, and preferably about 1-30 seconds.
In accordance with another aspect of the present invention, the coated base metal which is coated by a hot dip process is subjected to an air-knife process. In an air-knife process, the coated metal alloy is subjected to a high velocity fluid. The high velocity fluid removes surplus molten corrosion resistant metal alloy coating from the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating; smears the coated corrosion resistant metal alloy over the surface of the base metal, the surface of the intermediate barrier metal layer, and/or the surface of the previously applied metal alloy coating thereby reducing or eliminating pin holes or other uncoated surfaces; improves the grain size of the coated metal alloy; smooths and/or reducing lumps or ribs in the coated metal alloy; reduces the metal alloy coating thickness; and/or cools and/or hardens the molten metal alloy. In one embodiment of the invention, the air knife process uses a high velocity fluid which generally does not oxidize the corrosion resistant alloy. In one aspect of this embodiment, the fluid used in the air-knife process includes, but is not limited to, an inert or substantially inert gas such as, but not limited to, nitrogen, sulfur hexafluoride, carbon dioxide, hydrogen, noble gases, and/or hydrocarbons. In another embodiment of the invention, the high velocity fluid of the air-knife process is directed onto both sides of the coated base metal and at a direction which is not perpendicular to the surface of the coated base metal. In still another embodiment of the invention, the protective material on the surface of the molten metal alloy in the melting pot is eliminated when the air-knife process is used in conjunction with a coating process by immersion in molten alloy. When an air-knife process is used in conjunction with coating by immersion, the inert or substantially inert fluid inhibits or prevents dross formation and/or viscous oxide formation in the region in which the inert or substantially inert fluid contacts the molten metal alloy in the melting pot. The high velocity of the inert or substantially inert fluid also breaks up and/or pushes away dross or viscous oxides on the surface of the molten metal alloy thus forming a dross and oxide free region for the coated base metal to be removed from the melting pot. In yet another embodiment of the invention, the air-knife process includes one or more blast nozzles to direct a high velocity fluid toward the metal alloy coating on the surface of the base metal. In one aspect of this embodiment, the coated base metal is directed between two or more blast nozzles. In still yet another embodiment, the air-knife process at least partially causes molten metal alloy on the surface of the base metal to be directed back into the melting pot when the air-knife process is used in conjunction with an immersion coating process. In a further embodiment, one or more blast nozzles are adjustable so as to direct the high velocity fluid at various angles onto the surface of the coated base metal. In yet a further embodiment of the invention, one or more blast nozzles are partially or fully enclosed in a chamber, which chamber is designed to accumulate or trap at least a portion of the fluid after the fluid is directed toward the base metal. The accumulated fluid can then be recirculated back through the blast nozzles. In still a further embodiment of the invention, the air-knife process is used to control the thickness and/or quality of the molten metal alloy coating. In still yet a further embodiment of the invention, the base metal is exposed to the fluid from the air-knife process for a relatively short period of time. The time the base metal is exposed to the fluid is dependent on the speed of the moving base metal. Typically, the base metal is exposed to the fluid from the air-knife process for at least about 0.3 seconds, generally about 0.5-60 seconds, and preferably about 1-30 seconds.
In accordance with another aspect of the present invention, the coated base metal is cooled by a cooling process. Typically the coated base metal is cooled after being coated by a hot dip coating process. The coated base metal can be cooled by spraying with and/or subjecting the coated base metal to a cooling fluid and/or immersing the coated base metal in a cooling fluid. As previously stated, when an air-knife process is used, the coated base metal can be at least partially cooled by the fluid from the air-knife process. When the heated corrosion resistant metal alloy slowly cools, larger grain sizes and lower grain densities generally occur in the corrosion resistant metal alloy coating, and the corrosion resistant metal alloy coating typically forms a more reflective surface. When the heated corrosion resistant metal alloy rapidly cools, fine grain sizes and increased grain densities occur in the corrosion resistant metal alloy coating, and the corrosion resistant metal alloy coating forms a less reflective surface than a slowly cooled corrosion resistant alloy coating. Small grain sizes and higher grain densities in the corrosion resistant metal alloy coating typically result in a stronger bonding coating and greater corrosion resistance. In one embodiment of the invention, the cooling process is less than about two hours. In one aspect of this embodiment, the cooling process is less than about one hour. In another aspect of this embodiment, the cooling process is less than 10 minutes. In still another aspect of this embodiment, the cooling process is less than about 5 minutes. In another embodiment of the invention, a liquid or gas is jet sprayed onto the surface of the coated base metal to cool the metal alloy coating. In one aspect of this embodiment, the cooling fluid is water. In another aspect of this embodiment, the temperature of the cooling fluid is about 15-95xc2x0 C. In yet another aspect of this embodiment, the temperature of the cooling fluid is about 20-60xc2x0 C. In yet another aspect of this embodiment, the temperature of the cooling fluid is about ambient temperature (20-28xc2x0 C.). In still yet another aspect of this embodiment, the coated base metal is at least partially guided by a camel-back guide as the coated base metal is cooled by the spray jets. The camel-back guide is designed to minimize contact with the coated base metal thereby reducing the amount of metal alloy coating inadvertently removed from the base metal. In one aspect of this embodiment, the camel-back design allows cooling fluid to be applied to both sides of the coated base metal. In still another embodiment of the invention, the coated metal alloy is cooled by immersion in a cooling fluid. Typically, the coated base metal is directed into a cooling tank that contains a cooling fluid. In one aspect of this embodiment, the temperature of the cooling fluid in the cooling tank is maintained at a desired temperature by use of agitators, heat exchangers, and/or replenishment of cooling fluid. In another aspect of this embodiment, the temperature of the cooling fluid is about 15-95xc2x0 C. In yet another aspect of this embodiment, the temperature of the cooling fluid is about 20-60xc2x0 C. In yet another aspect of this embodiment, the temperature of the cooling fluid is about ambient temperature (20-28xc2x0 C.). In still yet another aspect of this embodiment, water is used as the cooling fluid. The oxygen in the water can cause discoloration of the metal alloy coating thereby reducing the reflectiveness of the metal alloy coating.
In accordance with another aspect of the invention, the coated base metal is passed through a leveler whereby the coated metal alloy is molded about the base metal, and/or smoothed. In one embodiment of the invention, a final coating thickness is obtained by the leveler. In another embodiment of the invention, the leveler includes a plurality of rollers. In yet another embodiment of the invention, the base metal is maintained at a tension as it is passed through the leveler.
In accordance with yet another aspect of the invention, the coated base metal is rolled into a coil for later processing or use.
In accordance with still another aspect of the invention, the coated base metal is sheared into specific length plates or strip for later use or immediate processing. In one embodiment of the invention, a shearing device shears a continuously moving coated base metal. In one aspect of this embodiment, the shearing device moves with the moving coated base metal when shearing.
In accordance with still yet another aspect of the present invention, the heat created intermetallic layer formed between the metal alloy coating and the surface of the base metal, surface of the intermediate barrier metal layer, and/or surface of a previously applied metal alloy coating is at least partially exposed. The exposed heat created intermetallic layer has been found to provide excellent corrosion resistance in a number of environments. The heat created intermetallic layer can be exposed by mechanical and/or chemical processes. In one embodiment of the invention, at least a portion of the metal alloy coating is removed by a mechanical process that includes, but is not limited to, grinding, melting, shearing and the like. In another embodiment of the invention, at least a portion of the metal alloy coating is removed by a chemical process which includes, but is not limited to, an oxidation process. The oxidation process at least partially removes the coated metal alloy and at least partially exposes the heat created intermetallic layer. The oxidation process includes the use of an oxidizing solution. In one aspect of this embodiment, the oxidation solution is selected to be autocatalytic in that the oxidation solution removes the metal alloy coating but does not or only very slowly removes the heat created intermetallic layer. In another aspect of this embodiment, the oxidation solution includes nitric acid and/or chromic acid. When nitric acid is included in the oxidation solution, the nitric acid concentration is generally about 5-60% by volume and typically about 10-25% by volume of the oxidation solution. In still another aspect of this embodiment, the oxidation solution includes copper sulfate. When copper sulfate is included in the oxidation solution, the copper sulfate is generally less than about 10% by volume, typically about 0.5-2% by volume of the oxidation solution, and preferably about 1% by volume of the oxidation solution. In yet another aspect of this embodiment, the exposure of the coated base metal to the oxidation solution in the oxidation process is generally less than about one hour; however, longer times can be used depending on the concentration and temperature of the oxidation solution, the type of metal alloy, the thickness of the metal alloy, and/or the degree of desired exposure of the heat created intermetallic layer. In one specific aspect, the exposure to the oxidation solution in the oxidation process is less than about ten minutes. In another specific aspect, the exposure to the oxidation solution in the oxidation process is less than about two minutes. In still another specific aspect, the exposure to the oxidation solution in the oxidation process is about 0.08-1.5 minutes. In a further aspect of this embodiment, after a sufficient amount of the heat created intermetallic layer is exposed by the oxidation solution, the oxidation solution is removed from the base metal. In still a further aspect this embodiment, the temperature of the oxidation solution is about 15-80xc2x0 C. In yet a further aspect this embodiment, the temperature of the oxidation solution is about 30-80xc2x0 C. In yet a further aspect this embodiment, the temperature of the oxidation solution is about 15-60xc2x0 C. In a further aspect this embodiment, the temperature of the oxidation solution is about 12-62xc2x0 C. In yet a further aspect this embodiment, the temperature of the oxidation solution is about 40-60xc2x0 C. In yet a further aspect this embodiment, the temperature of the oxidation solution is about 22-42xc2x0 C. In still a further aspect this embodiment, the temperature of the oxidation solution is about 32xc2x0 C. In still yet a further aspect of this embodiment, the oxidation solution is rinsed off after the intermetallic layer is exposed. In still another embodiment of the invention, the at least partial removal of the metal alloy coating is described in U.S. Pat. No. 5,397,652, which is incorporated herein.
In accordance with another aspect of the present invention, the exposed heat created intermetallic layer is passivated by a passivation process. The passivation process is designed to at least partially react with the heat created intermetallic layer and to form a thin corrosion resistant layer. The corrosion resistant layer exhibits improved corrosion resistant properties, improved abrasion resistance, improved hardness, improved formality, resists cracking, and/or has less reflective color as compared to a non-passified intermetallic layer. The passivation process includes the use of a passivation solution. In one embodiment of the invention, the passivation solution includes a nitrogen containing compound. In another embodiment of the invention, the passivation solution is the same as the oxidation solution, thus the oxidation/passivation solution removes the metal alloy to expose the heat created intermetallic layer and subsequently passifies the exposed heat created intermetallic layer to form the corrosion resistant layer. In one aspect of this embodiment, the oxidizing solution fully or substantially ceases to react with the intermetallic layer after the passivation later is formed (auto-catalytic). In another embodiment of the invention, the coated base metal material is passivated in a different tank from the oxidation solution. In yet another embodiment of the invention, the oxidation solution and/or passivation solution is rinsed off the coated base metal after the formation of the passivation layer. In still yet another embodiment of the present invention, the pacified intermetallic layer exhibits excellent formability characteristics. The formability of the base material having a pacified intermetallic layer on the surface of the base material exhibits improved formability characteristics over a tin metal alloy or a tin and zinc metal alloy coated base material. The improved formability is believed to be the result of the complete or partial removal of the tin metal alloy or tin and zinc metal alloy from the surface of the base material. The removal of the tin metal alloy or tin and zinc metal alloy reduces the thickness of the treated base material. The tin metal alloy or tin and zinc metal alloy is also less formable than many types of base metal such as, but not limited to, copper, copper alloys, aluminum, aluminum alloys. As a result, the reducing of the thickness of the coated base material and by partial or complete removal of a less formable metal layer, i.e. the tin metal alloy or tin and zinc metal alloy, results in formability. In yet another embodiment of the invention, the thickness of the passivation layer is at least about 0.1 micron. In still another embodiment of the invention, the thickness of the passivation layer is about 0.1-5 microns. In still another embodiment of the invention, the thickness of the passivation layer is up to about 1.5 microns.
In accordance with still another aspect of the present invention, the coated base metal is treated with a weathering agent to accelerate the weathering, discoloration of the surface of the metal alloy coating, and/or control the formation of white rust on the surface of the metal alloy coating. In one embodiment of the invention, the weathering material is applied to the metal alloy coating to oxidize the metal alloy coating surface, reduce the reflectivity of the metal alloy coating, and/or discolor the metal alloy coating. In another embodiment of the invention, the weathering material is an asphalt-based paint which causes accelerated weathering of the metal alloy coating when exposed to the atmosphere. The asphalt-based paint decreases the weathering time of the metal alloy coating. In one aspect of this embodiment, the asphalt paint is a petroleum-based paint which includes asphalt, titanium oxide, inert silicates, clay, carbon black or other free carbon and an anti-settling agent. In another aspect of this embodiment, the asphalt-based paint is applied at a thickness to form a semi-transparent or translucent layer over the metal alloy coating. In one specific aspect, the thickness of the asphalt-based paint is about 1-500 microns. In another specific aspect, the thickness of the asphalt-based paint is about 6-150 microns. In still another specific aspect, the thickness of the asphalt-based paint is about 6-123 microns. In yet another specific aspect, the thickness of the asphalt-based paint is about 12-50 microns. In still yet a further specific aspect, the thickness of the asphalt-based paint is about 12-25 microns. In still yet another embodiment of the invention, the weathering agent is dried by air drying and/or by heating lamps.
In accordance with yet another aspect of the present invention, the metal alloy or base metal coated with the metal alloy coating is immediately formed, or formed at a manufacturing site, or formed at a building site. In one embodiment of the invention, the metal alloy or coated base metal is formed into roofing materials such as disclosed in, but not limited to, gutter systems or roofing material which are illustrated in U.S. Pat. Nos. 4,987,716; 5001,881; 5,022,203; 5,259,166; and 5,301,474, all of which are incorporated herein by reference. In one aspect of this embodiment, the roofing materials are formed on site. In another embodiment of the invention, the metal alloy or coated base metal is formed into an automotive part such as, but not limited to a gasoline tank. In one aspect of this embodiment, the gasoline tank includes a first and second metal shell member. The two combined cavities of the shell members are combined to form an inner fuel receiving chamber which holds fuel within the receptacle. The abutting peripheral edges of the shell members are joined together and sealed to maintain the fuel within the inner petroleum receiving chamber. The two shell members may be joined in any of a number of ways that will securely prevent the shells from separating and petroleum from leaking from the interior chamber (i.e. welding, soldering and/or bonding the edges together). Such a fuel tank is illustrated in U.S. Pat. No. 5,455,122, which is incorporated herein by reference. In still another embodiment of the invention, the metal alloy is formed into a wire. In one aspect of this embodiment, the wire is used as a solder or welding wire to solder or weld together metals. In one specific aspect, the solder or welding wire is formulated to have excellent wetting properties which helps to ensure the formation of a high quality bond between metal materials. In another specific aspect, the solder or welding wire is formulated to have a low lead content. In still another specific aspect, the solder or welding wire can be used in standard soldering guns or welding apparatuses (i.e. ultrasonic welding, arc welding, gas welding, laser welding). In still yet another specific aspect, the solder has low dissolving activity with the welded metal materials. In a further specific aspect, the welding wire is a solid welding wire or a cored welding wire. In still another embodiment of the invention, the metal alloy exhibits excellent soldering or welding characteristics such that various electrodes including lead and/or no-lead containing solders and/or electrodes can be used to solder and/or weld the metal alloy or coated base metal.
In accordance with yet another aspect of the present invention, the metal alloy and/or coated base metal base material can be formed on site without the metal alloy cracking and/or flaking off.
In accordance with still another aspect of the present invention, the metal alloy is formed into a corrosion-resistant strip or sheet. In one embodiment of the invention, the metal alloy strip is formed by a roll forming process. In the roll forming process, a vat of molten metal alloy is provided. The molten alloy is then directed through a series of rollers until the desired thickness of the metal alloy strip or sheet is obtained.
The primary object of the present invention is the provision of a metal alloy having corrosion-resistant properties.
Another object of the present invention is the provision of a base metal coated with a metal alloy having corrosion resistant properties.
Yet another object of the present invention is the provision of a metal material at least partially formed from a metal alloy having corrosion resistant properties.
Still another object of the present invention is the provision of a metal alloy and/or coated base metal which is both corrosion-resistant and environmentally-friendly.
Still yet another object of the present invention is the provision of a coated base metal having a sufficient coating thickness to reduce or eliminate pinholes in the coating and/or which the shearing of the coating is inhibited when the coated base metal is formed.
Another object of the present invention is the provision of a coated base metal having a heat created intermetallic layer formed between the base metal and the metal alloy coating.
Yet another object of the present invention is the provision of a coated base metal coated by a hot dip process.
Still another object of the present invention is the provision of coating a base metal by a plating process.
Yet still another object of the present invention is the provision of a base metal coated by a continuous process.
Still yet another object of the present invention is the provision of a metal alloy or a coated base metal which is formed and sheared into various building and roofing components, automotive components, marine products, household materials, and other formed materials that are subsequently assembled on site or in a forming facility.
Another object of the present invention is the provision of a metal alloy or coated base metal that is corrosion-resistant and which can be formed into complex shapes and/or ornamental designs.
Another object of the present invention is the provision of a corrosion resistant metal alloy which includes a coloring agent to alter the color of the corrosion resistant metal alloy, a corrosion-resistance agent to improve the corrosion-resistance of the corrosion resistant metal alloy, a mechanical agent to improve the mechanical properties of the corrosion resistant metal alloy, a grain agent to positively affect grain refinement of the corrosion resistant metal alloy, an oxidation agent to reduce oxidation of the molten corrosion resistant metal alloy, an inhibiting agent to inhibit the crystallization of the corrosion resistant metal alloy, and/or a bonding agent to improve the bonding characteristics of the corrosion resistant metal alloy.
Still another object of the present invention is the provision of a corrosion resistant metal alloy which includes a majority of tin.
Yet another object of the present invention is the provision of a corrosion resistant metal alloy which includes a majority of tin and zinc.
Another object of the present invention is the provision of applying an intermediate barrier metal layer to the surface of the base metal prior to applying the corrosion resistant metal alloy coating.
Still another object of the present invention is the provision of a coated base metal or metal alloy which is formed into wire, wire solder and/or welding electrodes.
Still yet another object of the invention is the provision of a metal alloy and/or a coated base metal which is economical to produce.
Another object of the invention is the provision of a metal alloy and/or a coated base metal that can be soldered with conventional tin-lead solders or no-lead solders.
Yet another object of the present invention is the provision of pretreating the base metal prior to coating the base metal with a corrosion resistant alloy to remove oxides and/or foreign materials from the surface of the base metal.
Another object of the present invention is the provision of pickling the base metal to remove surface oxides on the base metal prior to coating the base metal with a metal alloy.
Yet another object of the present invention is the provision of chemically activating the base metal to remove surface oxides on the base metal prior to coating the base metal with a metal.
Still yet another object of the present invention is the provision of reducing the oxygen interaction with the base metal prior to and/or during the coating process.
Another object of the present invention is the provision of abrasively treating the surface of the base metal prior to coating the base metal with a metal alloy.
Still yet another object of the present invention is the provision of a metal alloy and/or a metal coating that is not highly reflective.
Yet another object of the present invention is the provision of a metal alloy and/or a metal coating for a base metal which has a low lead content.
Still yet another object of the present invention is the provision of using spray jets to spray molten metal alloy onto the surface of the base metal to coat the surface of the base metal.
Another object of the present invention is the provision of coating a metal alloy and/or a metal coating with a weathering agent to accelerate the dulling of the surface of the metal alloy.
Still another object of the present invention is the use of an air-knife process to control the thickness and quality of the metal alloy coating on the base metal.
Yet still another object of the present invention is the provision of cooling the metal alloy and/or a metal coating to form fine, high density grains which produce a strong bonding, corrosive-resistant, discolored coating.
Another object of the present invention is the provision of subjecting the coated base metal to an oxidation solution to at least partially remove the metal alloy from the base metal and to at least partially expose the heat created intermetallic layer.
Still another object of the present invention is the provision of subjecting the heat created intermetallic layer to a passivation solution to form a highly corrosion-resistant, non-reflective surface layer on the base metal.
Still yet another object of the present invention is the provision of a metal alloy coating which has superior corrosive characteristics permitting a thinner coating of the metal alloy to the base metal than that which is required for conventional terne coatings with the high lead content.
Still yet another object of the present invention is the provision of using spray jets which spray metal alloy onto the coating rollers and/or base metal surface to eliminate non-coated surfaces on the base metal.
Another object of the present invention is the indirect heating of the melting pot without use of heating coils or heating rods.
Another object of the present invention is the provision of a corrosion resistant metal alloy that can be coated on a number of different base metal compositions.
Yet another object of the present invention is the provision of a corrosion resistant metal alloy that can be coated a base metal having a number of different shapes.
Still another object of the present invention is the provision of providing a coated base metal which is formed by a continuous, hot dip process wherein the base metal has a controlled residence time when exposed to the molten metal alloy.
Still yet another object of the present invention is the provision of producing a highly corrosion-resistant metal alloy or coated base material that is economical to make.
These and other objects and advantages will become apparent to those skilled in the art upon the reading and following of this description taken together with the accompanied drawing.